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	$200.51	12.137%	$224.8459	$224.85	$224.85	$224.80
Purchase #2	$188.31	12.865%	$212.5361	$212.54	$212.55	$212.50
Purchase #3	$58.95	4.294%	$61.4813	$61.48	$61.50	$61.50
Purchase #4	$160.25	7.273%	$171.905	$171.91	$171.90	$171.90
Purchase #5	$134.90	12.139%	$151.2755	$151.28	$151.30	$151.30
Purchase #6	$17.34	6.311%	$18.4343	$18.43	$18.45	$18.40
Purchase #7	$129.30	13.517%	$146.7775	$146.78	$146.80	$146.80
7 purchase totals =	$889.56		$987.2556	$987.27	$987.35	$987.20