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	$213.33	7.605%	$229.5537	$229.55	$229.55	$229.60
Purchase #2	$250.75	5.137%	$263.631	$263.63	$263.65	$263.60
Purchase #3	$205.46	11.674%	$229.4454	$229.45	$229.45	$229.40
Purchase #4	$82.46	7.615%	$88.7393	$88.74	$88.75	$88.70
Purchase #5	$190.43	13.280%	$215.7191	$215.72	$215.70	$215.70
Purchase #6	$79.85	12.130%	$89.5358	$89.54	$89.55	$89.50
Purchase #7	$136.34	7.266%	$146.2465	$146.25	$146.25	$146.20
7 purchase totals =	$1,158.62		$1,262.8708	$1,262.88	$1,262.90	$1,262.70