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	$59.46	8.666%	$64.6128	$64.61	$64.60	$64.60
Purchase #2	$112.99	12.817%	$127.4719	$127.47	$127.45	$127.50
Purchase #3	$244.31	10.828%	$270.7639	$270.76	$270.75	$270.80
Purchase #4	$153.84	4.424%	$160.6459	$160.65	$160.65	$160.60
Purchase #5	$185.25	13.471%	$210.205	$210.21	$210.20	$210.20
Purchase #6	$220.97	11.701%	$246.8257	$246.83	$246.85	$246.80
Purchase #7	$40.56	6.111%	$43.0386	$43.04	$43.05	$43.00
7 purchase totals =	$1,017.38		$1,123.5638	$1,123.57	$1,123.55	$1,123.50