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	$127.98	4.764%	$134.077	$134.08	$134.10	$134.10
Purchase #2	$209.88	3.329%	$216.8669	$216.87	$216.85	$216.90
Purchase #3	$235.91	4.720%	$247.045	$247.05	$247.05	$247.00
Purchase #4	$162.35	6.459%	$172.8362	$172.84	$172.85	$172.80
Purchase #5	$59.69	12.871%	$67.3727	$67.37	$67.35	$67.40
Purchase #6	$138.43	7.329%	$148.5755	$148.58	$148.60	$148.60
Purchase #7	$25.43	12.706%	$28.6611	$28.66	$28.65	$28.70
7 purchase totals =	$959.67		$1,015.4344	$1,015.45	$1,015.45	$1,015.50