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	$179.78	6.623%	$191.6868	$191.69	$191.70	$191.70
Purchase #2	$96.52	3.740%	$100.1298	$100.13	$100.15	$100.10
Purchase #3	$231.95	13.175%	$262.5094	$262.51	$262.50	$262.50
Purchase #4	$209.85	9.514%	$229.8151	$229.82	$229.80	$229.80
Purchase #5	$57.37	5.605%	$60.5856	$60.59	$60.60	$60.60
Purchase #6	$35.80	9.593%	$39.2343	$39.23	$39.25	$39.20
Purchase #7	$194.27	8.407%	$210.6023	$210.60	$210.60	$210.60
7 purchase totals =	$1,005.54		$1,094.5633	$1,094.57	$1,094.60	$1,094.50