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	$145.30	7.178%	$155.7296	$155.73	$155.75	$155.70
Purchase #2	$178.69	13.835%	$203.4118	$203.41	$203.40	$203.40
Purchase #3	$45.89	5.725%	$48.5172	$48.52	$48.50	$48.50
Purchase #4	$174.51	12.586%	$196.4738	$196.47	$196.45	$196.50
Purchase #5	$52.54	13.294%	$59.5247	$59.52	$59.50	$59.50
Purchase #6	$166.87	10.376%	$184.1844	$184.18	$184.20	$184.20
Purchase #7	$68.31	13.708%	$77.6739	$77.67	$77.65	$77.70
7 purchase totals =	$832.11		$925.5154	$925.50	$925.45	$925.50