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	$198.94	7.306%	$213.4746	$213.47	$213.45	$213.50
Purchase #2	$182.69	12.146%	$204.8795	$204.88	$204.90	$204.90
Purchase #3	$185.37	4.782%	$194.2344	$194.23	$194.25	$194.20
Purchase #4	$241.33	5.208%	$253.8985	$253.90	$253.90	$253.90
Purchase #5	$125.83	3.680%	$130.4605	$130.46	$130.45	$130.50
Purchase #6	$188.90	12.398%	$212.3198	$212.32	$212.30	$212.30
Purchase #7	$233.50	9.277%	$255.1618	$255.16	$255.15	$255.20
7 purchase totals =	$1,356.56		$1,464.4291	$1,464.42	$1,464.40	$1,464.50