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	$175.52	9.301%	$191.8451	$191.85	$191.85	$191.80
Purchase #2	$118.37	8.599%	$128.5486	$128.55	$128.55	$128.50
Purchase #3	$92.37	3.298%	$95.4164	$95.42	$95.40	$95.40
Purchase #4	$158.95	10.491%	$175.6254	$175.63	$175.65	$175.60
Purchase #5	$229.71	12.766%	$259.0348	$259.03	$259.05	$259.00
Purchase #6	$223.34	4.661%	$233.7499	$233.75	$233.75	$233.70
Purchase #7	$81.72	9.293%	$89.3142	$89.31	$89.30	$89.30
7 purchase totals =	$1,079.98		$1,173.5344	$1,173.54	$1,173.55	$1,173.30