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	$99.76	11.339%	$111.0718	$111.07	$111.05	$111.10
Purchase #2	$27.53	4.753%	$28.8385	$28.84	$28.85	$28.80
Purchase #3	$239.51	6.462%	$254.9871	$254.99	$255.00	$255.00
Purchase #4	$114.79	13.760%	$130.5851	$130.59	$130.60	$130.60
Purchase #5	$82.91	5.517%	$87.4841	$87.48	$87.50	$87.50
Purchase #6	$108.56	3.552%	$112.4161	$112.42	$112.40	$112.40
Purchase #7	$89.79	5.793%	$94.9915	$94.99	$95.00	$95.00
7 purchase totals =	$762.85		$820.3742	$820.38	$820.40	$820.40