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	$185.60	7.683%	$199.8596	$199.86	$199.85	$199.90
Purchase #2	$166.33	13.318%	$188.4818	$188.48	$188.50	$188.50
Purchase #3	$87.81	4.294%	$91.5806	$91.58	$91.60	$91.60
Purchase #4	$111.81	13.246%	$126.6204	$126.62	$126.60	$126.60
Purchase #5	$172.87	6.482%	$184.0754	$184.08	$184.10	$184.10
Purchase #6	$92.82	6.134%	$98.5136	$98.51	$98.50	$98.50
Purchase #7	$209.60	9.602%	$229.7258	$229.73	$229.75	$229.70
7 purchase totals =	$1,026.84		$1,118.8572	$1,118.86	$1,118.90	$1,118.90