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	$82.28	5.360%	$86.6902	$86.69	$86.70	$86.70
Purchase #2	$184.89	13.864%	$210.5231	$210.52	$210.50	$210.50
Purchase #3	$22.72	5.468%	$23.9623	$23.96	$23.95	$24.00
Purchase #4	$19.63	5.586%	$20.7265	$20.73	$20.75	$20.70
Purchase #5	$112.89	5.673%	$119.2942	$119.29	$119.30	$119.30
Purchase #6	$235.33	8.826%	$256.1002	$256.10	$256.10	$256.10
Purchase #7	$29.87	7.152%	$32.0063	$32.01	$32.00	$32.00
7 purchase totals =	$687.61		$749.3028	$749.30	$749.30	$749.30