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	$221.33	9.709%	$242.8189	$242.82	$242.80	$242.80
Purchase #2	$88.42	11.425%	$98.522	$98.52	$98.50	$98.50
Purchase #3	$174.44	9.290%	$190.6455	$190.65	$190.65	$190.60
Purchase #4	$97.57	9.190%	$106.5367	$106.54	$106.55	$106.50
Purchase #5	$99.71	8.760%	$108.4446	$108.44	$108.45	$108.40
Purchase #6	$54.82	11.782%	$61.2789	$61.28	$61.30	$61.30
Purchase #7	$242.33	8.587%	$263.1389	$263.14	$263.15	$263.10
7 purchase totals =	$978.62		$1,071.3855	$1,071.39	$1,071.40	$1,071.20