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	$227.38	3.615%	$235.5998	$235.60	$235.60	$235.60
Purchase #2	$107.80	3.453%	$111.5223	$111.52	$111.50	$111.50
Purchase #3	$137.34	3.388%	$141.9931	$141.99	$142.00	$142.00
Purchase #4	$96.69	7.415%	$103.8596	$103.86	$103.85	$103.90
Purchase #5	$28.84	11.637%	$32.1961	$32.20	$32.20	$32.20
Purchase #6	$205.42	9.372%	$224.672	$224.67	$224.65	$224.70
Purchase #7	$151.69	12.148%	$170.1173	$170.12	$170.10	$170.10
7 purchase totals =	$955.16		$1,019.9602	$1,019.96	$1,019.90	$1,020.00