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	$198.33	10.406%	$218.9682	$218.97	$218.95	$219.00
Purchase #2	$28.84	8.623%	$31.3269	$31.33	$31.35	$31.30
Purchase #3	$230.37	11.179%	$256.1231	$256.12	$256.10	$256.10
Purchase #4	$200.99	10.249%	$221.5895	$221.59	$221.60	$221.60
Purchase #5	$173.91	13.788%	$197.8887	$197.89	$197.90	$197.90
Purchase #6	$47.95	13.502%	$54.4242	$54.42	$54.40	$54.40
Purchase #7	$61.86	8.574%	$67.1639	$67.16	$67.15	$67.20
7 purchase totals =	$942.25		$1,047.4845	$1,047.48	$1,047.45	$1,047.50