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	$50.28	4.872%	$52.7296	$52.73	$52.75	$52.70
Purchase #2	$87.42	3.677%	$90.6344	$90.63	$90.65	$90.60
Purchase #3	$208.92	7.735%	$225.08	$225.08	$225.10	$225.10
Purchase #4	$231.34	8.752%	$251.5869	$251.59	$251.60	$251.60
Purchase #5	$208.31	7.499%	$223.9312	$223.93	$223.95	$223.90
Purchase #6	$162.59	12.136%	$182.3219	$182.32	$182.30	$182.30
Purchase #7	$81.28	9.676%	$89.1447	$89.14	$89.15	$89.10
7 purchase totals =	$1,030.14		$1,115.4287	$1,115.42	$1,115.50	$1,115.30