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	$68.28	11.841%	$76.365	$76.37	$76.35	$76.40
Purchase #2	$33.59	5.806%	$35.5402	$35.54	$35.55	$35.50
Purchase #3	$184.56	8.629%	$200.4857	$200.49	$200.50	$200.50
Purchase #4	$242.72	4.428%	$253.4676	$253.47	$253.45	$253.50
Purchase #5	$56.55	5.539%	$59.6823	$59.68	$59.70	$59.70
Purchase #6	$113.27	10.702%	$125.3922	$125.39	$125.40	$125.40
Purchase #7	$207.32	8.689%	$225.334	$225.33	$225.35	$225.30
7 purchase totals =	$906.29		$976.2670	$976.27	$976.30	$976.30