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	$10.41	6.819%	$11.1199	$11.12	$11.10	$11.10
Purchase #2	$57.95	12.333%	$65.097	$65.10	$65.10	$65.10
Purchase #3	$212.45	4.821%	$222.6922	$222.69	$222.70	$222.70
Purchase #4	$98.55	4.643%	$103.1257	$103.13	$103.15	$103.10
Purchase #5	$19.49	8.563%	$21.1589	$21.16	$21.15	$21.20
Purchase #6	$117.79	11.549%	$131.3936	$131.39	$131.40	$131.40
Purchase #7	$185.25	10.211%	$204.1659	$204.17	$204.15	$204.20
7 purchase totals =	$701.89		$758.7532	$758.76	$758.75	$758.80