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	$218.28	8.813%	$237.517	$237.52	$237.50	$237.50
Purchase #2	$25.61	11.131%	$28.4606	$28.46	$28.45	$28.50
Purchase #3	$211.48	13.512%	$240.0552	$240.06	$240.05	$240.10
Purchase #4	$108.41	9.662%	$118.8846	$118.88	$118.90	$118.90
Purchase #5	$99.58	10.243%	$109.78	$109.78	$109.80	$109.80
Purchase #6	$93.91	6.620%	$100.1268	$100.13	$100.15	$100.10
Purchase #7	$150.78	13.837%	$171.6434	$171.64	$171.65	$171.60
7 purchase totals =	$908.05		$1,006.4676	$1,006.47	$1,006.50	$1,006.50