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	$138.43	9.749%	$151.9255	$151.93	$151.95	$151.90
Purchase #2	$54.63	12.147%	$61.2659	$61.27	$61.25	$61.30
Purchase #3	$73.67	5.337%	$77.6018	$77.60	$77.60	$77.60
Purchase #4	$166.77	13.137%	$188.6786	$188.68	$188.70	$188.70
Purchase #5	$210.30	6.332%	$223.6162	$223.62	$223.60	$223.60
Purchase #6	$52.34	4.268%	$54.5739	$54.57	$54.55	$54.60
Purchase #7	$207.84	10.417%	$229.4907	$229.49	$229.50	$229.50
7 purchase totals =	$903.98		$987.1526	$987.16	$987.15	$987.20