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	$101.64	9.455%	$111.2501	$111.25	$111.25	$111.30
Purchase #2	$152.72	12.482%	$171.7825	$171.78	$171.80	$171.80
Purchase #3	$137.63	13.228%	$155.8357	$155.84	$155.85	$155.80
Purchase #4	$101.75	5.799%	$107.6505	$107.65	$107.65	$107.70
Purchase #5	$125.65	11.732%	$140.3913	$140.39	$140.40	$140.40
Purchase #6	$137.80	6.800%	$147.1704	$147.17	$147.15	$147.20
Purchase #7	$222.76	11.283%	$247.894	$247.89	$247.90	$247.90
7 purchase totals =	$979.95		$1,081.9745	$1,081.97	$1,082.00	$1,082.10