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	$226.35	11.819%	$253.1023	$253.10	$253.10	$253.10
Purchase #2	$95.77	11.174%	$106.4713	$106.47	$106.45	$106.50
Purchase #3	$28.89	9.259%	$31.5649	$31.56	$31.55	$31.60
Purchase #4	$146.88	12.533%	$165.2885	$165.29	$165.30	$165.30
Purchase #5	$136.70	9.728%	$149.9982	$150.00	$150.00	$150.00
Purchase #6	$146.81	4.539%	$153.4737	$153.47	$153.45	$153.50
Purchase #7	$148.81	4.435%	$155.4097	$155.41	$155.40	$155.40
7 purchase totals =	$930.21		$1,015.3086	$1,015.30	$1,015.25	$1,015.40