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	$96.26	8.535%	$104.4758	$104.48	$104.50	$104.50
Purchase #2	$238.33	4.804%	$249.7794	$249.78	$249.80	$249.80
Purchase #3	$236.32	7.110%	$253.1224	$253.12	$253.10	$253.10
Purchase #4	$26.30	7.686%	$28.3214	$28.32	$28.30	$28.30
Purchase #5	$99.84	11.261%	$111.083	$111.08	$111.10	$111.10
Purchase #6	$229.54	3.139%	$236.7453	$236.75	$236.75	$236.70
Purchase #7	$83.48	9.350%	$91.2854	$91.29	$91.30	$91.30
7 purchase totals =	$1,010.07		$1,074.8127	$1,074.82	$1,074.85	$1,074.80