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	$242.68	8.539%	$263.4024	$263.40	$263.40	$263.40
Purchase #2	$246.37	9.357%	$269.4228	$269.42	$269.40	$269.40
Purchase #3	$65.55	9.776%	$71.9582	$71.96	$71.95	$72.00
Purchase #4	$227.83	11.715%	$254.5203	$254.52	$254.50	$254.50
Purchase #5	$52.93	12.438%	$59.5134	$59.51	$59.50	$59.50
Purchase #6	$27.31	4.248%	$28.4701	$28.47	$28.45	$28.50
Purchase #7	$43.61	7.694%	$46.9654	$46.97	$46.95	$47.00
7 purchase totals =	$906.28		$994.2526	$994.25	$994.15	$994.30