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	$79.38	4.574%	$83.0108	$83.01	$83.00	$83.00
Purchase #2	$96.29	4.276%	$100.4074	$100.41	$100.40	$100.40
Purchase #3	$184.68	8.118%	$199.6723	$199.67	$199.65	$199.70
Purchase #4	$134.74	13.413%	$152.8127	$152.81	$152.80	$152.80
Purchase #5	$184.50	3.120%	$190.2564	$190.26	$190.25	$190.30
Purchase #6	$224.97	8.355%	$243.7662	$243.77	$243.75	$243.80
Purchase #7	$42.44	6.245%	$45.0904	$45.09	$45.10	$45.10
7 purchase totals =	$947.00		$1,015.0162	$1,015.02	$1,014.95	$1,015.10