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	$109.89	4.236%	$114.5449	$114.54	$114.55	$114.50
Purchase #2	$225.53	3.323%	$233.0244	$233.02	$233.00	$233.00
Purchase #3	$82.61	7.355%	$88.686	$88.69	$88.70	$88.70
Purchase #4	$146.57	6.621%	$156.2744	$156.27	$156.25	$156.30
Purchase #5	$55.42	7.442%	$59.5444	$59.54	$59.55	$59.50
Purchase #6	$130.26	10.153%	$143.4853	$143.49	$143.50	$143.50
Purchase #7	$5.40	9.555%	$5.916	$5.92	$5.90	$5.90
7 purchase totals =	$755.68		$801.4754	$801.47	$801.45	$801.40