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	$48.84	8.289%	$52.8883	$52.89	$52.90	$52.90
Purchase #2	$172.66	5.763%	$182.6104	$182.61	$182.60	$182.60
Purchase #3	$121.67	13.307%	$137.8606	$137.86	$137.85	$137.90
Purchase #4	$79.95	13.829%	$91.0063	$91.01	$91.00	$91.00
Purchase #5	$117.63	8.554%	$127.6921	$127.69	$127.70	$127.70
Purchase #6	$223.80	10.255%	$246.7507	$246.75	$246.75	$246.80
Purchase #7	$198.76	11.846%	$222.3051	$222.31	$222.30	$222.30
7 purchase totals =	$963.31		$1,061.1135	$1,061.12	$1,061.10	$1,061.20