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	$180.58	8.805%	$196.4801	$196.48	$196.50	$196.50
Purchase #2	$91.77	8.680%	$99.7356	$99.74	$99.75	$99.70
Purchase #3	$54.85	13.869%	$62.4571	$62.46	$62.45	$62.50
Purchase #4	$124.41	6.634%	$132.6634	$132.66	$132.65	$132.70
Purchase #5	$84.80	7.651%	$91.288	$91.29	$91.30	$91.30
Purchase #6	$104.46	13.678%	$118.748	$118.75	$118.75	$118.70
Purchase #7	$243.98	6.746%	$260.4389	$260.44	$260.45	$260.40
7 purchase totals =	$884.85		$961.8111	$961.82	$961.85	$961.80