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	$88.48	5.324%	$93.1907	$93.19	$93.20	$93.20
Purchase #2	$99.44	7.226%	$106.6255	$106.63	$106.65	$106.60
Purchase #3	$112.33	9.611%	$123.126	$123.13	$123.15	$123.10
Purchase #4	$209.40	6.322%	$222.6383	$222.64	$222.65	$222.60
Purchase #5	$149.32	4.380%	$155.8602	$155.86	$155.85	$155.90
Purchase #6	$149.59	12.503%	$168.2932	$168.29	$168.30	$168.30
Purchase #7	$125.28	9.826%	$137.59	$137.59	$137.60	$137.60
7 purchase totals =	$933.84		$1,007.3239	$1,007.33	$1,007.40	$1,007.30