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	$68.45	13.435%	$77.6463	$77.65	$77.65	$77.60
Purchase #2	$19.84	7.705%	$21.3687	$21.37	$21.35	$21.40
Purchase #3	$78.68	12.347%	$88.3946	$88.39	$88.40	$88.40
Purchase #4	$109.63	11.740%	$122.5006	$122.50	$122.50	$122.50
Purchase #5	$75.86	12.632%	$85.4426	$85.44	$85.45	$85.40
Purchase #6	$88.95	3.578%	$92.1326	$92.13	$92.15	$92.10
Purchase #7	$12.74	13.142%	$14.4143	$14.41	$14.40	$14.40
7 purchase totals =	$454.15		$501.8997	$501.89	$501.90	$501.80