Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$175.44	7.369%	$188.3682	$188.37	$188.35	$188.40
Purchase #2	$108.83	3.655%	$112.8077	$112.81	$112.80	$112.80
Purchase #3	$215.73	3.155%	$222.5363	$222.54	$222.55	$222.50
Purchase #4	$112.39	10.112%	$123.7549	$123.75	$123.75	$123.80
Purchase #5	$165.99	11.314%	$184.7701	$184.77	$184.75	$184.80
Purchase #6	$162.78	10.319%	$179.5773	$179.58	$179.60	$179.60
Purchase #7	$239.36	10.130%	$263.6072	$263.61	$263.60	$263.60
7 purchase totals =	$1,180.52		$1,275.4217	$1,275.43	$1,275.40	$1,275.50