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	$93.77	4.825%	$98.2944	$98.29	$98.30	$98.30
Purchase #2	$130.78	13.469%	$148.3948	$148.39	$148.40	$148.40
Purchase #3	$94.50	12.709%	$106.51	$106.51	$106.50	$106.50
Purchase #4	$218.43	10.190%	$240.688	$240.69	$240.70	$240.70
Purchase #5	$156.78	9.768%	$172.0943	$172.09	$172.10	$172.10
Purchase #6	$218.98	6.706%	$233.6648	$233.66	$233.65	$233.70
Purchase #7	$78.46	12.842%	$88.5358	$88.54	$88.55	$88.50
7 purchase totals =	$991.70		$1,088.1821	$1,088.17	$1,088.20	$1,088.20