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	$147.61	11.449%	$164.5099	$164.51	$164.50	$164.50
Purchase #2	$58.28	5.543%	$61.5105	$61.51	$61.50	$61.50
Purchase #3	$159.52	9.307%	$174.3665	$174.37	$174.35	$174.40
Purchase #4	$218.31	12.676%	$245.983	$245.98	$246.00	$246.00
Purchase #5	$220.58	10.343%	$243.3946	$243.39	$243.40	$243.40
Purchase #6	$34.56	7.554%	$37.1707	$37.17	$37.15	$37.20
Purchase #7	$85.93	9.340%	$93.9559	$93.96	$93.95	$94.00
7 purchase totals =	$924.79		$1,020.8911	$1,020.89	$1,020.85	$1,021.00