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	$27.66	4.632%	$28.9412	$28.94	$28.95	$28.90
Purchase #2	$230.30	6.218%	$244.6201	$244.62	$244.60	$244.60
Purchase #3	$165.61	13.412%	$187.8216	$187.82	$187.80	$187.80
Purchase #4	$158.90	6.347%	$168.9854	$168.99	$169.00	$169.00
Purchase #5	$33.90	10.731%	$37.5378	$37.54	$37.55	$37.50
Purchase #6	$185.59	7.432%	$199.383	$199.38	$199.40	$199.40
Purchase #7	$205.72	10.594%	$227.514	$227.51	$227.50	$227.50
7 purchase totals =	$1,007.68		$1,094.8031	$1,094.80	$1,094.80	$1,094.70