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	$146.27	4.113%	$152.2861	$152.29	$152.30	$152.30
Purchase #2	$158.35	9.514%	$173.4154	$173.42	$173.40	$173.40
Purchase #3	$79.61	4.409%	$83.12	$83.12	$83.10	$83.10
Purchase #4	$86.67	11.438%	$96.5833	$96.58	$96.60	$96.60
Purchase #5	$108.56	13.617%	$123.3426	$123.34	$123.35	$123.30
Purchase #6	$136.71	5.245%	$143.8804	$143.88	$143.90	$143.90
Purchase #7	$110.53	12.623%	$124.4822	$124.48	$124.50	$124.50
7 purchase totals =	$826.70		$897.1100	$897.11	$897.15	$897.10