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	$210.83	5.446%	$222.3118	$222.31	$222.30	$222.30
Purchase #2	$18.31	4.665%	$19.1642	$19.16	$19.15	$19.20
Purchase #3	$146.43	8.616%	$159.0464	$159.05	$159.05	$159.00
Purchase #4	$95.89	5.238%	$100.9127	$100.91	$100.90	$100.90
Purchase #5	$101.70	4.237%	$106.009	$106.01	$106.00	$106.00
Purchase #6	$121.61	12.168%	$136.4075	$136.41	$136.40	$136.40
Purchase #7	$173.32	8.228%	$187.5808	$187.58	$187.60	$187.60
7 purchase totals =	$868.09		$931.4324	$931.43	$931.40	$931.40