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	$165.73	12.699%	$186.7761	$186.78	$186.80	$186.80
Purchase #2	$142.72	13.701%	$162.2741	$162.27	$162.25	$162.30
Purchase #3	$41.40	11.708%	$46.2471	$46.25	$46.25	$46.20
Purchase #4	$194.31	4.790%	$203.6174	$203.62	$203.60	$203.60
Purchase #5	$146.47	7.140%	$156.928	$156.93	$156.95	$156.90
Purchase #6	$217.59	13.214%	$246.3423	$246.34	$246.35	$246.30
Purchase #7	$57.51	3.166%	$59.3308	$59.33	$59.35	$59.30
7 purchase totals =	$965.73		$1,061.5158	$1,061.52	$1,061.55	$1,061.40