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	$205.55	6.287%	$218.4729	$218.47	$218.45	$218.50
Purchase #2	$21.95	13.624%	$24.9405	$24.94	$24.95	$24.90
Purchase #3	$191.73	9.733%	$210.3911	$210.39	$210.40	$210.40
Purchase #4	$236.64	11.652%	$264.2133	$264.21	$264.20	$264.20
Purchase #5	$100.67	3.138%	$103.829	$103.83	$103.85	$103.80
Purchase #6	$154.32	7.447%	$165.8122	$165.81	$165.80	$165.80
Purchase #7	$133.98	4.154%	$139.5455	$139.55	$139.55	$139.50
7 purchase totals =	$1,044.84		$1,127.2045	$1,127.20	$1,127.20	$1,127.10