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	$92.80	13.580%	$105.4022	$105.40	$105.40	$105.40
Purchase #2	$244.98	12.138%	$274.7157	$274.72	$274.70	$274.70
Purchase #3	$180.35	12.524%	$202.937	$202.94	$202.95	$202.90
Purchase #4	$228.67	9.711%	$250.8761	$250.88	$250.90	$250.90
Purchase #5	$48.30	13.626%	$54.8814	$54.88	$54.90	$54.90
Purchase #6	$137.28	10.577%	$151.8001	$151.80	$151.80	$151.80
Purchase #7	$67.79	4.274%	$70.6873	$70.69	$70.70	$70.70
7 purchase totals =	$1,000.17		$1,111.2998	$1,111.31	$1,111.35	$1,111.30