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	$159.90	10.285%	$176.3457	$176.35	$176.35	$176.30
Purchase #2	$244.98	11.494%	$273.138	$273.14	$273.15	$273.10
Purchase #3	$53.87	13.708%	$61.2545	$61.25	$61.25	$61.30
Purchase #4	$232.41	10.127%	$255.9462	$255.95	$255.95	$255.90
Purchase #5	$86.43	4.477%	$90.2995	$90.30	$90.30	$90.30
Purchase #6	$193.42	6.862%	$206.6925	$206.69	$206.70	$206.70
Purchase #7	$221.46	10.621%	$244.9813	$244.98	$245.00	$245.00
7 purchase totals =	$1,192.47		$1,308.6577	$1,308.66	$1,308.70	$1,308.60