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	$47.31	13.208%	$53.5587	$53.56	$53.55	$53.60
Purchase #2	$241.54	12.315%	$271.2857	$271.29	$271.30	$271.30
Purchase #3	$117.70	6.415%	$125.2505	$125.25	$125.25	$125.30
Purchase #4	$143.33	6.401%	$152.5046	$152.50	$152.50	$152.50
Purchase #5	$79.94	12.396%	$89.8494	$89.85	$89.85	$89.80
Purchase #6	$50.69	9.865%	$55.6906	$55.69	$55.70	$55.70
Purchase #7	$175.57	5.240%	$184.7699	$184.77	$184.75	$184.80
7 purchase totals =	$856.08		$932.9094	$932.91	$932.90	$933.00