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	$149.78	10.181%	$165.0291	$165.03	$165.05	$165.00
Purchase #2	$152.71	4.685%	$159.8645	$159.86	$159.85	$159.90
Purchase #3	$31.35	4.360%	$32.7169	$32.72	$32.70	$32.70
Purchase #4	$36.35	11.751%	$40.6215	$40.62	$40.60	$40.60
Purchase #5	$167.35	3.626%	$173.4181	$173.42	$173.40	$173.40
Purchase #6	$219.87	8.379%	$238.2929	$238.29	$238.30	$238.30
Purchase #7	$193.46	4.861%	$202.8641	$202.86	$202.85	$202.90
7 purchase totals =	$950.87		$1,012.8071	$1,012.80	$1,012.75	$1,012.80