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	$33.59	5.472%	$35.428	$35.43	$35.45	$35.40
Purchase #2	$172.51	13.244%	$195.3572	$195.36	$195.35	$195.40
Purchase #3	$19.73	5.423%	$20.8	$20.80	$20.80	$20.80
Purchase #4	$168.33	13.205%	$190.558	$190.56	$190.55	$190.60
Purchase #5	$156.77	6.223%	$166.5258	$166.53	$166.55	$166.50
Purchase #6	$215.58	7.481%	$231.7075	$231.71	$231.70	$231.70
Purchase #7	$226.38	9.131%	$247.0508	$247.05	$247.05	$247.10
7 purchase totals =	$992.89		$1,087.4273	$1,087.44	$1,087.45	$1,087.50