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	$194.30	3.288%	$200.6886	$200.69	$200.70	$200.70
Purchase #2	$156.54	10.400%	$172.8202	$172.82	$172.80	$172.80
Purchase #3	$58.40	12.874%	$65.9184	$65.92	$65.90	$65.90
Purchase #4	$199.57	4.463%	$208.4768	$208.48	$208.50	$208.50
Purchase #5	$116.58	10.821%	$129.1951	$129.20	$129.20	$129.20
Purchase #6	$81.84	10.817%	$90.6926	$90.69	$90.70	$90.70
Purchase #7	$86.61	10.502%	$95.7058	$95.71	$95.70	$95.70
7 purchase totals =	$893.84		$963.4975	$963.51	$963.50	$963.50