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	$194.38	3.389%	$200.9675	$200.97	$200.95	$201.00
Purchase #2	$79.26	3.232%	$81.8217	$81.82	$81.80	$81.80
Purchase #3	$155.51	11.517%	$173.4201	$173.42	$173.40	$173.40
Purchase #4	$60.51	3.248%	$62.4754	$62.48	$62.50	$62.50
Purchase #5	$82.76	7.720%	$89.1491	$89.15	$89.15	$89.10
Purchase #6	$178.64	10.520%	$197.4329	$197.43	$197.45	$197.40
Purchase #7	$36.56	11.401%	$40.7282	$40.73	$40.75	$40.70
7 purchase totals =	$787.62		$845.9949	$846.00	$846.00	$845.90