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	$17.84	8.625%	$19.3787	$19.38	$19.40	$19.40
Purchase #2	$17.73	10.230%	$19.5438	$19.54	$19.55	$19.50
Purchase #3	$230.90	7.142%	$247.3909	$247.39	$247.40	$247.40
Purchase #4	$62.59	5.108%	$65.7871	$65.79	$65.80	$65.80
Purchase #5	$225.65	10.864%	$250.1646	$250.16	$250.15	$250.20
Purchase #6	$144.33	4.520%	$150.8537	$150.85	$150.85	$150.90
Purchase #7	$243.83	7.584%	$262.3221	$262.32	$262.30	$262.30
7 purchase totals =	$942.87		$1,015.4409	$1,015.43	$1,015.45	$1,015.50