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	$210.27	11.574%	$234.6066	$234.61	$234.60	$234.60
Purchase #2	$171.69	9.244%	$187.561	$187.56	$187.55	$187.60
Purchase #3	$87.80	11.460%	$97.8619	$97.86	$97.85	$97.90
Purchase #4	$72.59	11.126%	$80.6664	$80.67	$80.65	$80.70
Purchase #5	$66.50	6.798%	$71.0207	$71.02	$71.00	$71.00
Purchase #6	$160.69	13.227%	$181.9445	$181.94	$181.95	$181.90
Purchase #7	$39.69	7.184%	$42.5413	$42.54	$42.55	$42.50
7 purchase totals =	$809.23		$896.2024	$896.20	$896.15	$896.20