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	$147.45	13.869%	$167.8998	$167.90	$167.90	$167.90
Purchase #2	$149.46	11.367%	$166.4491	$166.45	$166.45	$166.40
Purchase #3	$224.49	8.513%	$243.6008	$243.60	$243.60	$243.60
Purchase #4	$206.80	12.805%	$233.2807	$233.28	$233.30	$233.30
Purchase #5	$68.99	13.753%	$78.4782	$78.48	$78.50	$78.50
Purchase #6	$99.46	4.668%	$104.1028	$104.10	$104.10	$104.10
Purchase #7	$22.67	11.524%	$25.2825	$25.28	$25.30	$25.30
7 purchase totals =	$919.32		$1,019.0939	$1,019.09	$1,019.15	$1,019.10