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	$49.39	10.743%	$54.696	$54.70	$54.70	$54.70
Purchase #2	$152.86	9.546%	$167.452	$167.45	$167.45	$167.50
Purchase #3	$81.90	7.290%	$87.8705	$87.87	$87.85	$87.90
Purchase #4	$124.67	4.765%	$130.6105	$130.61	$130.60	$130.60
Purchase #5	$136.59	10.580%	$151.0412	$151.04	$151.05	$151.00
Purchase #6	$140.39	3.698%	$145.5816	$145.58	$145.60	$145.60
Purchase #7	$162.89	13.559%	$184.9763	$184.98	$185.00	$185.00
7 purchase totals =	$848.69		$922.2281	$922.23	$922.25	$922.30