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	$125.46	13.313%	$142.1625	$142.16	$142.15	$142.20
Purchase #2	$82.30	9.149%	$89.8296	$89.83	$89.85	$89.80
Purchase #3	$161.95	4.649%	$169.4791	$169.48	$169.50	$169.50
Purchase #4	$105.41	11.272%	$117.2918	$117.29	$117.30	$117.30
Purchase #5	$235.38	9.733%	$258.2895	$258.29	$258.30	$258.30
Purchase #6	$230.63	4.414%	$240.81	$240.81	$240.80	$240.80
Purchase #7	$199.69	7.866%	$215.3976	$215.40	$215.40	$215.40
7 purchase totals =	$1,140.82		$1,233.2601	$1,233.26	$1,233.30	$1,233.30