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	$245.45	9.401%	$268.5248	$268.52	$268.50	$268.50
Purchase #2	$197.68	10.858%	$219.1441	$219.14	$219.15	$219.10
Purchase #3	$157.91	7.866%	$170.3312	$170.33	$170.35	$170.30
Purchase #4	$168.83	13.427%	$191.4988	$191.50	$191.50	$191.50
Purchase #5	$231.82	10.697%	$256.6178	$256.62	$256.60	$256.60
Purchase #6	$64.54	12.420%	$72.5559	$72.56	$72.55	$72.60
Purchase #7	$197.29	11.424%	$219.8284	$219.83	$219.85	$219.80
7 purchase totals =	$1,263.52		$1,398.5010	$1,398.50	$1,398.50	$1,398.40