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	$32.74	3.693%	$33.9491	$33.95	$33.95	$33.90
Purchase #2	$104.73	6.114%	$111.1332	$111.13	$111.15	$111.10
Purchase #3	$248.95	9.454%	$272.4857	$272.49	$272.50	$272.50
Purchase #4	$214.30	9.517%	$234.6949	$234.69	$234.70	$234.70
Purchase #5	$73.56	5.848%	$77.8618	$77.86	$77.85	$77.90
Purchase #6	$78.51	9.586%	$86.036	$86.04	$86.05	$86.00
Purchase #7	$94.69	4.380%	$98.8374	$98.84	$98.85	$98.80
7 purchase totals =	$847.48		$914.9981	$915.00	$915.05	$914.90