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	$197.90	6.342%	$210.4508	$210.45	$210.45	$210.50
Purchase #2	$150.59	7.497%	$161.8797	$161.88	$161.90	$161.90
Purchase #3	$45.31	6.808%	$48.3947	$48.39	$48.40	$48.40
Purchase #4	$180.31	8.782%	$196.1448	$196.14	$196.15	$196.10
Purchase #5	$80.53	13.457%	$91.3669	$91.37	$91.35	$91.40
Purchase #6	$61.52	4.463%	$64.2656	$64.27	$64.25	$64.30
Purchase #7	$193.68	12.609%	$218.1011	$218.10	$218.10	$218.10
7 purchase totals =	$909.84		$990.6036	$990.60	$990.60	$990.70