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	$22.83	11.542%	$25.465	$25.47	$25.45	$25.50
Purchase #2	$106.46	4.319%	$111.058	$111.06	$111.05	$111.10
Purchase #3	$89.70	7.816%	$96.711	$96.71	$96.70	$96.70
Purchase #4	$195.79	13.768%	$222.7464	$222.75	$222.75	$222.70
Purchase #5	$214.94	11.342%	$239.3185	$239.32	$239.30	$239.30
Purchase #6	$166.31	9.644%	$182.3489	$182.35	$182.35	$182.30
Purchase #7	$155.29	11.170%	$172.6359	$172.64	$172.65	$172.60
7 purchase totals =	$951.32		$1,050.2837	$1,050.30	$1,050.25	$1,050.20