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	$77.61	9.671%	$85.1157	$85.12	$85.10	$85.10
Purchase #2	$245.46	13.630%	$278.9162	$278.92	$278.90	$278.90
Purchase #3	$249.70	11.534%	$278.5004	$278.50	$278.50	$278.50
Purchase #4	$85.89	12.799%	$96.8831	$96.88	$96.90	$96.90
Purchase #5	$145.77	6.616%	$155.4141	$155.41	$155.40	$155.40
Purchase #6	$143.29	5.530%	$151.2139	$151.21	$151.20	$151.20
Purchase #7	$134.70	5.202%	$141.7071	$141.71	$141.70	$141.70
7 purchase totals =	$1,082.42		$1,187.7505	$1,187.75	$1,187.70	$1,187.70