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	$175.50	8.303%	$190.0718	$190.07	$190.05	$190.10
Purchase #2	$38.67	11.811%	$43.2373	$43.24	$43.25	$43.20
Purchase #3	$40.77	6.251%	$43.3185	$43.32	$43.30	$43.30
Purchase #4	$151.72	3.322%	$156.7601	$156.76	$156.75	$156.80
Purchase #5	$46.72	3.214%	$48.2216	$48.22	$48.20	$48.20
Purchase #6	$121.69	8.312%	$131.8049	$131.80	$131.80	$131.80
Purchase #7	$11.64	7.718%	$12.5384	$12.54	$12.55	$12.50
7 purchase totals =	$586.71		$625.9526	$625.95	$625.90	$625.90