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	$95.28	4.378%	$99.4514	$99.45	$99.45	$99.50
Purchase #2	$217.88	11.283%	$242.4634	$242.46	$242.45	$242.50
Purchase #3	$250.31	6.447%	$266.4475	$266.45	$266.45	$266.40
Purchase #4	$203.38	9.744%	$223.1973	$223.20	$223.20	$223.20
Purchase #5	$208.94	10.754%	$231.4094	$231.41	$231.40	$231.40
Purchase #6	$229.64	4.341%	$239.6087	$239.61	$239.60	$239.60
Purchase #7	$95.68	13.657%	$108.747	$108.75	$108.75	$108.70
7 purchase totals =	$1,301.11		$1,411.3247	$1,411.33	$1,411.30	$1,411.30