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	$142.61	10.842%	$158.0718	$158.07	$158.05	$158.10
Purchase #2	$85.25	6.346%	$90.66	$90.66	$90.65	$90.70
Purchase #3	$175.90	6.237%	$186.8709	$186.87	$186.85	$186.90
Purchase #4	$72.29	5.737%	$76.4373	$76.44	$76.45	$76.40
Purchase #5	$35.85	3.580%	$37.1334	$37.13	$37.15	$37.10
Purchase #6	$86.64	8.543%	$94.0417	$94.04	$94.05	$94.00
Purchase #7	$144.48	8.293%	$156.4617	$156.46	$156.45	$156.50
7 purchase totals =	$743.02		$799.6768	$799.67	$799.65	$799.70