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	$143.73	7.805%	$154.9481	$154.95	$154.95	$154.90
Purchase #2	$17.34	10.645%	$19.1858	$19.19	$19.20	$19.20
Purchase #3	$185.35	12.234%	$208.0257	$208.03	$208.05	$208.00
Purchase #4	$180.74	4.251%	$188.4233	$188.42	$188.40	$188.40
Purchase #5	$119.39	10.127%	$131.4806	$131.48	$131.50	$131.50
Purchase #6	$223.83	7.736%	$241.1455	$241.15	$241.15	$241.10
Purchase #7	$218.69	4.656%	$228.8722	$228.87	$228.85	$228.90
7 purchase totals =	$1,089.07		$1,172.0812	$1,172.09	$1,172.10	$1,172.00