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	$149.26	6.116%	$158.3887	$158.39	$158.40	$158.40
Purchase #2	$170.35	5.278%	$179.3411	$179.34	$179.35	$179.30
Purchase #3	$189.58	13.810%	$215.761	$215.76	$215.75	$215.80
Purchase #4	$54.61	3.718%	$56.6404	$56.64	$56.65	$56.60
Purchase #5	$165.54	5.502%	$174.648	$174.65	$174.65	$174.60
Purchase #6	$215.59	7.433%	$231.6148	$231.61	$231.60	$231.60
Purchase #7	$66.57	6.681%	$71.0175	$71.02	$71.00	$71.00
7 purchase totals =	$1,011.50		$1,087.4115	$1,087.41	$1,087.40	$1,087.30