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	$90.97	10.420%	$100.4491	$100.45	$100.45	$100.40
Purchase #2	$45.99	4.165%	$47.9055	$47.91	$47.90	$47.90
Purchase #3	$229.28	5.511%	$241.9156	$241.92	$241.90	$241.90
Purchase #4	$131.67	11.808%	$147.2176	$147.22	$147.20	$147.20
Purchase #5	$151.51	8.794%	$164.8338	$164.83	$164.85	$164.80
Purchase #6	$221.90	10.638%	$245.5057	$245.51	$245.50	$245.50
Purchase #7	$101.80	3.587%	$105.4516	$105.45	$105.45	$105.50
7 purchase totals =	$973.12		$1,053.2789	$1,053.29	$1,053.25	$1,053.20