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	$184.88	11.375%	$205.9101	$205.91	$205.90	$205.90
Purchase #2	$209.47	6.115%	$222.2791	$222.28	$222.30	$222.30
Purchase #3	$36.46	8.680%	$39.6247	$39.62	$39.60	$39.60
Purchase #4	$189.86	9.677%	$208.2328	$208.23	$208.25	$208.20
Purchase #5	$89.92	10.146%	$99.0433	$99.04	$99.05	$99.00
Purchase #6	$19.91	13.533%	$22.6044	$22.60	$22.60	$22.60
Purchase #7	$232.86	5.229%	$245.0362	$245.04	$245.05	$245.00
7 purchase totals =	$963.36		$1,042.7306	$1,042.72	$1,042.75	$1,042.60