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	$105.83	9.737%	$116.1347	$116.13	$116.15	$116.10
Purchase #2	$35.35	13.490%	$40.1187	$40.12	$40.10	$40.10
Purchase #3	$33.38	13.174%	$37.7775	$37.78	$37.80	$37.80
Purchase #4	$243.71	9.713%	$267.3816	$267.38	$267.40	$267.40
Purchase #5	$55.93	6.428%	$59.5252	$59.53	$59.55	$59.50
Purchase #6	$39.56	12.478%	$44.4963	$44.50	$44.50	$44.50
Purchase #7	$27.76	10.558%	$30.6909	$30.69	$30.70	$30.70
7 purchase totals =	$541.52		$596.1249	$596.13	$596.20	$596.10