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	$57.33	13.303%	$64.9566	$64.96	$64.95	$65.00
Purchase #2	$166.72	3.598%	$172.7186	$172.72	$172.70	$172.70
Purchase #3	$220.82	11.298%	$245.7682	$245.77	$245.75	$245.80
Purchase #4	$56.96	13.630%	$64.7236	$64.72	$64.70	$64.70
Purchase #5	$48.43	5.789%	$51.2336	$51.23	$51.25	$51.20
Purchase #6	$248.72	7.216%	$266.6676	$266.67	$266.65	$266.70
Purchase #7	$161.88	3.708%	$167.8825	$167.88	$167.90	$167.90
7 purchase totals =	$960.86		$1,033.9507	$1,033.95	$1,033.90	$1,034.00