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	$209.61	6.813%	$223.8907	$223.89	$223.90	$223.90
Purchase #2	$55.28	4.849%	$57.9605	$57.96	$57.95	$58.00
Purchase #3	$47.60	11.548%	$53.0968	$53.10	$53.10	$53.10
Purchase #4	$141.96	5.740%	$150.1085	$150.11	$150.10	$150.10
Purchase #5	$218.70	7.380%	$234.8401	$234.84	$234.85	$234.80
Purchase #6	$199.42	8.225%	$215.8223	$215.82	$215.80	$215.80
Purchase #7	$188.64	12.677%	$212.5539	$212.55	$212.55	$212.60
7 purchase totals =	$1,061.21		$1,148.2728	$1,148.27	$1,148.25	$1,148.30