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	$198.84	3.146%	$205.0955	$205.10	$205.10	$205.10
Purchase #2	$53.76	10.437%	$59.3709	$59.37	$59.35	$59.40
Purchase #3	$137.69	6.171%	$146.1868	$146.19	$146.20	$146.20
Purchase #4	$121.55	8.187%	$131.5013	$131.50	$131.50	$131.50
Purchase #5	$172.91	4.450%	$180.6045	$180.60	$180.60	$180.60
Purchase #6	$244.54	6.666%	$260.841	$260.84	$260.85	$260.80
Purchase #7	$121.52	12.179%	$136.3199	$136.32	$136.30	$136.30
7 purchase totals =	$1,050.81		$1,119.9199	$1,119.92	$1,119.90	$1,119.90