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	$46.52	7.715%	$50.109	$50.11	$50.10	$50.10
Purchase #2	$28.86	12.549%	$32.4816	$32.48	$32.50	$32.50
Purchase #3	$195.99	9.539%	$214.6855	$214.69	$214.70	$214.70
Purchase #4	$196.40	11.592%	$219.1667	$219.17	$219.15	$219.20
Purchase #5	$168.41	13.557%	$191.2413	$191.24	$191.25	$191.20
Purchase #6	$31.51	3.456%	$32.599	$32.60	$32.60	$32.60
Purchase #7	$250.62	11.347%	$279.0579	$279.06	$279.05	$279.10
7 purchase totals =	$918.31		$1,019.3410	$1,019.35	$1,019.35	$1,019.40