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	$6.81	9.749%	$7.4739	$7.47	$7.45	$7.50
Purchase #2	$103.93	13.676%	$118.1435	$118.14	$118.15	$118.10
Purchase #3	$52.83	5.258%	$55.6078	$55.61	$55.60	$55.60
Purchase #4	$56.33	4.650%	$58.9493	$58.95	$58.95	$58.90
Purchase #5	$151.86	5.179%	$159.7248	$159.72	$159.70	$159.70
Purchase #6	$105.95	4.783%	$111.0176	$111.02	$111.00	$111.00
Purchase #7	$178.86	9.786%	$196.3632	$196.36	$196.35	$196.40
7 purchase totals =	$656.57		$707.2801	$707.27	$707.20	$707.20