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	$88.32	4.317%	$92.1328	$92.13	$92.15	$92.10
Purchase #2	$189.84	11.805%	$212.2506	$212.25	$212.25	$212.30
Purchase #3	$225.40	13.344%	$255.4774	$255.48	$255.50	$255.50
Purchase #4	$215.48	12.271%	$241.9216	$241.92	$241.90	$241.90
Purchase #5	$209.93	6.476%	$223.5251	$223.53	$223.55	$223.50
Purchase #6	$59.87	8.228%	$64.7961	$64.80	$64.80	$64.80
Purchase #7	$12.59	7.408%	$13.5227	$13.52	$13.50	$13.50
7 purchase totals =	$1,001.43		$1,103.6263	$1,103.63	$1,103.65	$1,103.60