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	$180.72	10.745%	$200.1384	$200.14	$200.15	$200.10
Purchase #2	$160.29	12.672%	$180.6019	$180.60	$180.60	$180.60
Purchase #3	$194.60	4.585%	$203.5224	$203.52	$203.50	$203.50
Purchase #4	$180.46	11.243%	$200.7491	$200.75	$200.75	$200.70
Purchase #5	$93.91	6.223%	$99.754	$99.75	$99.75	$99.80
Purchase #6	$152.25	13.370%	$172.6058	$172.61	$172.60	$172.60
Purchase #7	$241.60	9.121%	$263.6363	$263.64	$263.65	$263.60
7 purchase totals =	$1,203.83		$1,321.0079	$1,321.01	$1,321.00	$1,320.90