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	$163.44	12.601%	$184.0351	$184.04	$184.05	$184.00
Purchase #2	$184.62	6.591%	$196.7883	$196.79	$196.80	$196.80
Purchase #3	$133.80	13.839%	$152.3166	$152.32	$152.30	$152.30
Purchase #4	$243.87	4.256%	$254.2491	$254.25	$254.25	$254.20
Purchase #5	$117.28	12.230%	$131.6233	$131.62	$131.60	$131.60
Purchase #6	$118.67	6.492%	$126.3741	$126.37	$126.35	$126.40
Purchase #7	$30.95	4.449%	$32.327	$32.33	$32.35	$32.30
7 purchase totals =	$992.63		$1,077.7135	$1,077.72	$1,077.70	$1,077.60