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	$32.84	13.254%	$37.1926	$37.19	$37.20	$37.20
Purchase #2	$48.48	4.402%	$50.6141	$50.61	$50.60	$50.60
Purchase #3	$30.40	7.185%	$32.5842	$32.58	$32.60	$32.60
Purchase #4	$89.71	3.133%	$92.5206	$92.52	$92.50	$92.50
Purchase #5	$233.60	12.529%	$262.8677	$262.87	$262.85	$262.90
Purchase #6	$246.58	7.217%	$264.3757	$264.38	$264.40	$264.40
Purchase #7	$127.61	5.701%	$134.885	$134.89	$134.90	$134.90
7 purchase totals =	$809.22		$875.0399	$875.04	$875.05	$875.10