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	$248.56	7.433%	$267.0355	$267.04	$267.05	$267.00
Purchase #2	$151.45	9.538%	$165.8953	$165.90	$165.90	$165.90
Purchase #3	$35.93	3.108%	$37.0467	$37.05	$37.05	$37.00
Purchase #4	$92.32	7.723%	$99.4499	$99.45	$99.45	$99.40
Purchase #5	$55.59	7.334%	$59.667	$59.67	$59.65	$59.70
Purchase #6	$96.62	12.240%	$108.4463	$108.45	$108.45	$108.40
Purchase #7	$122.41	7.475%	$131.5601	$131.56	$131.55	$131.60
7 purchase totals =	$802.88		$869.1008	$869.12	$869.10	$869.00