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	$236.73	11.472%	$263.8877	$263.89	$263.90	$263.90
Purchase #2	$64.61	10.496%	$71.3915	$71.39	$71.40	$71.40
Purchase #3	$171.95	10.749%	$190.4329	$190.43	$190.45	$190.40
Purchase #4	$129.63	11.192%	$144.1382	$144.14	$144.15	$144.10
Purchase #5	$40.96	4.586%	$42.8384	$42.84	$42.85	$42.80
Purchase #6	$102.36	8.793%	$111.3605	$111.36	$111.35	$111.40
Purchase #7	$203.47	8.768%	$221.3102	$221.31	$221.30	$221.30
7 purchase totals =	$949.71		$1,045.3594	$1,045.36	$1,045.40	$1,045.30