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	$55.48	13.287%	$62.8516	$62.85	$62.85	$62.90
Purchase #2	$62.93	13.342%	$71.3261	$71.33	$71.35	$71.30
Purchase #3	$53.88	13.831%	$61.3321	$61.33	$61.35	$61.30
Purchase #4	$98.70	11.134%	$109.6893	$109.69	$109.70	$109.70
Purchase #5	$93.69	3.440%	$96.9129	$96.91	$96.90	$96.90
Purchase #6	$21.97	10.580%	$24.2944	$24.29	$24.30	$24.30
Purchase #7	$102.67	8.329%	$111.2214	$111.22	$111.20	$111.20
7 purchase totals =	$489.32		$537.6278	$537.62	$537.65	$537.60