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	$67.38	10.670%	$74.5694	$74.57	$74.55	$74.60
Purchase #2	$169.33	6.577%	$180.4668	$180.47	$180.45	$180.50
Purchase #3	$85.68	5.427%	$90.3299	$90.33	$90.35	$90.30
Purchase #4	$238.92	3.438%	$247.1341	$247.13	$247.15	$247.10
Purchase #5	$184.51	8.827%	$200.7967	$200.80	$200.80	$200.80
Purchase #6	$168.73	6.773%	$180.1581	$180.16	$180.15	$180.20
Purchase #7	$231.31	10.224%	$254.9591	$254.96	$254.95	$255.00
7 purchase totals =	$1,145.86		$1,228.4141	$1,228.42	$1,228.40	$1,228.50