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	$199.34	10.685%	$220.6395	$220.64	$220.65	$220.60
Purchase #2	$52.52	5.761%	$55.5457	$55.55	$55.55	$55.50
Purchase #3	$105.87	4.850%	$111.0047	$111.00	$111.00	$111.00
Purchase #4	$178.40	12.610%	$200.8962	$200.90	$200.90	$200.90
Purchase #5	$237.79	8.150%	$257.1699	$257.17	$257.15	$257.20
Purchase #6	$31.56	4.561%	$32.9995	$33.00	$33.00	$33.00
Purchase #7	$212.27	13.591%	$241.1196	$241.12	$241.10	$241.10
7 purchase totals =	$1,017.75		$1,119.3751	$1,119.38	$1,119.35	$1,119.30