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	$150.55	3.404%	$155.6747	$155.67	$155.65	$155.70
Purchase #2	$159.47	8.787%	$173.4826	$173.48	$173.50	$173.50
Purchase #3	$163.95	13.369%	$185.8685	$185.87	$185.85	$185.90
Purchase #4	$249.39	6.143%	$264.71	$264.71	$264.70	$264.70
Purchase #5	$76.48	11.691%	$85.4213	$85.42	$85.40	$85.40
Purchase #6	$241.27	3.718%	$250.2404	$250.24	$250.25	$250.20
Purchase #7	$153.94	3.171%	$158.8214	$158.82	$158.80	$158.80
7 purchase totals =	$1,195.05		$1,274.2189	$1,274.21	$1,274.15	$1,274.20