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	$33.52	11.403%	$37.3423	$37.34	$37.35	$37.30
Purchase #2	$89.26	13.467%	$101.2806	$101.28	$101.30	$101.30
Purchase #3	$143.94	6.755%	$153.6631	$153.66	$153.65	$153.70
Purchase #4	$163.90	12.148%	$183.8106	$183.81	$183.80	$183.80
Purchase #5	$164.94	13.781%	$187.6704	$187.67	$187.65	$187.70
Purchase #6	$138.37	10.254%	$152.5585	$152.56	$152.55	$152.60
Purchase #7	$187.93	11.384%	$209.324	$209.32	$209.30	$209.30
7 purchase totals =	$921.86		$1,025.6495	$1,025.64	$1,025.60	$1,025.70