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	$143.96	8.142%	$155.6812	$155.68	$155.70	$155.70
Purchase #2	$27.35	13.758%	$31.1128	$31.11	$31.10	$31.10
Purchase #3	$47.53	5.758%	$50.2668	$50.27	$50.25	$50.30
Purchase #4	$35.91	3.467%	$37.155	$37.16	$37.15	$37.20
Purchase #5	$151.28	3.443%	$156.4886	$156.49	$156.50	$156.50
Purchase #6	$6.60	11.756%	$7.3759	$7.38	$7.40	$7.40
Purchase #7	$147.45	10.657%	$163.1637	$163.16	$163.15	$163.20
7 purchase totals =	$560.08		$601.2440	$601.25	$601.25	$601.40