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	$78.94	5.826%	$83.539	$83.54	$83.55	$83.50
Purchase #2	$68.39	10.321%	$75.4485	$75.45	$75.45	$75.40
Purchase #3	$188.43	6.207%	$200.1259	$200.13	$200.15	$200.10
Purchase #4	$213.46	7.631%	$229.7491	$229.75	$229.75	$229.70
Purchase #5	$139.83	10.400%	$154.3723	$154.37	$154.35	$154.40
Purchase #6	$10.29	5.520%	$10.858	$10.86	$10.85	$10.90
Purchase #7	$187.55	12.800%	$211.5564	$211.56	$211.55	$211.60
7 purchase totals =	$886.89		$965.6492	$965.66	$965.65	$965.60