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	$59.33	10.309%	$65.4463	$65.45	$65.45	$65.40
Purchase #2	$244.70	12.656%	$275.6692	$275.67	$275.65	$275.70
Purchase #3	$58.40	12.148%	$65.4944	$65.49	$65.50	$65.50
Purchase #4	$63.58	9.865%	$69.8522	$69.85	$69.85	$69.90
Purchase #5	$176.34	11.162%	$196.0231	$196.02	$196.00	$196.00
Purchase #6	$129.84	5.376%	$136.8202	$136.82	$136.80	$136.80
Purchase #7	$78.99	5.570%	$83.3897	$83.39	$83.40	$83.40
7 purchase totals =	$811.18		$892.6951	$892.69	$892.65	$892.70