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	$87.72	12.668%	$98.8324	$98.83	$98.85	$98.80
Purchase #2	$172.96	7.251%	$185.5013	$185.50	$185.50	$185.50
Purchase #3	$225.50	13.430%	$255.7847	$255.78	$255.80	$255.80
Purchase #4	$212.37	4.628%	$222.1985	$222.20	$222.20	$222.20
Purchase #5	$14.52	11.225%	$16.1499	$16.15	$16.15	$16.10
Purchase #6	$137.57	13.675%	$156.3827	$156.38	$156.40	$156.40
Purchase #7	$164.56	12.505%	$185.1382	$185.14	$185.15	$185.10
7 purchase totals =	$1,015.20		$1,119.9877	$1,119.98	$1,120.05	$1,119.90