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	$187.29	3.437%	$193.7272	$193.73	$193.75	$193.70
Purchase #2	$235.53	5.274%	$247.9519	$247.95	$247.95	$248.00
Purchase #3	$167.59	12.591%	$188.6913	$188.69	$188.70	$188.70
Purchase #4	$196.63	9.351%	$215.0169	$215.02	$215.00	$215.00
Purchase #5	$85.42	6.392%	$90.88	$90.88	$90.90	$90.90
Purchase #6	$193.25	13.723%	$219.7697	$219.77	$219.75	$219.80
Purchase #7	$148.94	6.652%	$158.8475	$158.85	$158.85	$158.80
7 purchase totals =	$1,214.65		$1,314.8845	$1,314.89	$1,314.90	$1,314.90