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	$194.52	7.203%	$208.5313	$208.53	$208.55	$208.50
Purchase #2	$99.37	3.569%	$102.9165	$102.92	$102.90	$102.90
Purchase #3	$52.69	13.528%	$59.8179	$59.82	$59.80	$59.80
Purchase #4	$102.79	8.220%	$111.2393	$111.24	$111.25	$111.20
Purchase #5	$212.81	9.563%	$233.161	$233.16	$233.15	$233.20
Purchase #6	$114.70	9.346%	$125.4199	$125.42	$125.40	$125.40
Purchase #7	$69.72	13.648%	$79.2354	$79.24	$79.25	$79.20
7 purchase totals =	$846.60		$920.3213	$920.33	$920.30	$920.20