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	$123.73	6.255%	$131.4693	$131.47	$131.45	$131.50
Purchase #2	$29.48	9.734%	$32.3496	$32.35	$32.35	$32.30
Purchase #3	$172.72	13.523%	$196.0769	$196.08	$196.10	$196.10
Purchase #4	$172.27	10.402%	$190.1895	$190.19	$190.20	$190.20
Purchase #5	$167.65	10.852%	$185.8434	$185.84	$185.85	$185.80
Purchase #6	$89.25	8.379%	$96.7283	$96.73	$96.75	$96.70
Purchase #7	$180.72	5.568%	$190.7825	$190.78	$190.80	$190.80
7 purchase totals =	$935.82		$1,023.4395	$1,023.44	$1,023.50	$1,023.40