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	$130.31	12.251%	$146.2743	$146.27	$146.25	$146.30
Purchase #2	$73.34	12.563%	$82.5537	$82.55	$82.55	$82.60
Purchase #3	$105.65	3.426%	$109.2696	$109.27	$109.25	$109.30
Purchase #4	$126.39	4.153%	$131.639	$131.64	$131.65	$131.60
Purchase #5	$150.74	10.299%	$166.2647	$166.26	$166.25	$166.30
Purchase #6	$220.37	10.689%	$243.9253	$243.93	$243.95	$243.90
Purchase #7	$182.79	11.654%	$204.0923	$204.09	$204.10	$204.10
7 purchase totals =	$989.59		$1,084.0189	$1,084.01	$1,084.00	$1,084.10