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	$86.94	8.570%	$94.3908	$94.39	$94.40	$94.40
Purchase #2	$67.29	8.362%	$72.9168	$72.92	$72.90	$72.90
Purchase #3	$131.65	11.272%	$146.4896	$146.49	$146.50	$146.50
Purchase #4	$9.50	9.585%	$10.4106	$10.41	$10.40	$10.40
Purchase #5	$211.89	11.616%	$236.5031	$236.50	$236.50	$236.50
Purchase #6	$139.36	7.564%	$149.9012	$149.90	$149.90	$149.90
Purchase #7	$82.47	10.746%	$91.3322	$91.33	$91.35	$91.30
7 purchase totals =	$729.10		$801.9443	$801.94	$801.95	$801.90