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	$92.69	11.295%	$103.1593	$103.16	$103.15	$103.20
Purchase #2	$165.96	10.525%	$183.4273	$183.43	$183.45	$183.40
Purchase #3	$165.52	9.425%	$181.1203	$181.12	$181.10	$181.10
Purchase #4	$170.72	8.601%	$185.4036	$185.40	$185.40	$185.40
Purchase #5	$88.72	4.746%	$92.9307	$92.93	$92.95	$92.90
Purchase #6	$120.65	7.666%	$129.899	$129.90	$129.90	$129.90
Purchase #7	$220.47	12.351%	$247.7002	$247.70	$247.70	$247.70
7 purchase totals =	$1,024.73		$1,123.6404	$1,123.64	$1,123.65	$1,123.60