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	$93.61	4.811%	$98.1136	$98.11	$98.10	$98.10
Purchase #2	$91.85	13.102%	$103.8842	$103.88	$103.90	$103.90
Purchase #3	$40.39	8.174%	$43.6915	$43.69	$43.70	$43.70
Purchase #4	$106.53	3.731%	$110.5046	$110.50	$110.50	$110.50
Purchase #5	$29.70	13.272%	$33.6418	$33.64	$33.65	$33.60
Purchase #6	$36.43	4.447%	$38.05	$38.05	$38.05	$38.10
Purchase #7	$177.87	4.366%	$185.6358	$185.64	$185.65	$185.60
7 purchase totals =	$576.38		$613.5215	$613.51	$613.55	$613.50