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	$239.92	9.424%	$262.5301	$262.53	$262.55	$262.50
Purchase #2	$42.41	7.229%	$45.4758	$45.48	$45.50	$45.50
Purchase #3	$158.94	7.718%	$171.207	$171.21	$171.20	$171.20
Purchase #4	$39.34	5.456%	$41.4864	$41.49	$41.50	$41.50
Purchase #5	$108.75	10.218%	$119.8621	$119.86	$119.85	$119.90
Purchase #6	$235.92	7.706%	$254.1	$254.10	$254.10	$254.10
Purchase #7	$71.62	11.111%	$79.5777	$79.58	$79.60	$79.60
7 purchase totals =	$896.90		$974.2391	$974.25	$974.30	$974.30