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	$48.36	11.314%	$53.8315	$53.83	$53.85	$53.80
Purchase #2	$147.46	3.428%	$152.5149	$152.51	$152.50	$152.50
Purchase #3	$247.37	11.265%	$275.2362	$275.24	$275.25	$275.20
Purchase #4	$224.47	11.699%	$250.7307	$250.73	$250.75	$250.70
Purchase #5	$19.35	4.212%	$20.165	$20.17	$20.15	$20.20
Purchase #6	$125.31	12.604%	$141.1041	$141.10	$141.10	$141.10
Purchase #7	$199.61	8.538%	$216.6527	$216.65	$216.65	$216.70
7 purchase totals =	$1,011.93		$1,110.2351	$1,110.23	$1,110.25	$1,110.20