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	$196.76	6.637%	$209.819	$209.82	$209.80	$209.80
Purchase #2	$208.50	4.530%	$217.9451	$217.95	$217.95	$217.90
Purchase #3	$248.89	8.832%	$270.872	$270.87	$270.85	$270.90
Purchase #4	$247.44	9.816%	$271.7287	$271.73	$271.75	$271.70
Purchase #5	$89.60	13.789%	$101.9549	$101.95	$101.95	$102.00
Purchase #6	$190.26	3.330%	$196.5957	$196.60	$196.60	$196.60
Purchase #7	$223.49	6.596%	$238.2314	$238.23	$238.25	$238.20
7 purchase totals =	$1,404.94		$1,507.1468	$1,507.15	$1,507.15	$1,507.10