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	$113.41	5.407%	$119.5421	$119.54	$119.55	$119.50
Purchase #2	$72.28	13.824%	$82.272	$82.27	$82.25	$82.30
Purchase #3	$28.52	13.505%	$32.3716	$32.37	$32.35	$32.40
Purchase #4	$190.33	5.469%	$200.7391	$200.74	$200.75	$200.70
Purchase #5	$12.73	4.427%	$13.2936	$13.29	$13.30	$13.30
Purchase #6	$57.95	4.350%	$60.4708	$60.47	$60.45	$60.50
Purchase #7	$53.87	8.586%	$58.4953	$58.50	$58.50	$58.50
7 purchase totals =	$529.09		$567.1845	$567.18	$567.15	$567.20