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	$154.94	11.126%	$172.1786	$172.18	$172.20	$172.20
Purchase #2	$64.60	10.872%	$71.6233	$71.62	$71.60	$71.60
Purchase #3	$167.31	11.114%	$185.9048	$185.90	$185.90	$185.90
Purchase #4	$197.40	13.533%	$224.1141	$224.11	$224.10	$224.10
Purchase #5	$168.86	7.110%	$180.8659	$180.87	$180.85	$180.90
Purchase #6	$137.74	6.373%	$146.5182	$146.52	$146.50	$146.50
Purchase #7	$185.31	13.193%	$209.7579	$209.76	$209.75	$209.80
7 purchase totals =	$1,076.16		$1,190.9628	$1,190.96	$1,190.90	$1,191.00