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	$191.76	13.624%	$217.8854	$217.89	$217.90	$217.90
Purchase #2	$184.76	8.585%	$200.6216	$200.62	$200.60	$200.60
Purchase #3	$5.59	3.569%	$5.7895	$5.79	$5.80	$5.80
Purchase #4	$40.31	6.225%	$42.8193	$42.82	$42.80	$42.80
Purchase #5	$238.28	5.475%	$251.3258	$251.33	$251.35	$251.30
Purchase #6	$30.26	7.128%	$32.4169	$32.42	$32.40	$32.40
Purchase #7	$152.44	12.261%	$171.1307	$171.13	$171.15	$171.10
7 purchase totals =	$843.40		$921.9892	$922.00	$922.00	$921.90