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	$79.76	13.668%	$90.6616	$90.66	$90.65	$90.70
Purchase #2	$80.29	12.690%	$90.4788	$90.48	$90.50	$90.50
Purchase #3	$35.94	8.109%	$38.8544	$38.85	$38.85	$38.90
Purchase #4	$175.49	10.286%	$193.5409	$193.54	$193.55	$193.50
Purchase #5	$198.92	8.594%	$216.0152	$216.02	$216.00	$216.00
Purchase #6	$197.81	3.787%	$205.3011	$205.30	$205.30	$205.30
Purchase #7	$223.83	7.841%	$241.3805	$241.38	$241.40	$241.40
7 purchase totals =	$992.04		$1,076.2325	$1,076.23	$1,076.25	$1,076.30