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	$210.82	7.573%	$226.7854	$226.79	$226.80	$226.80
Purchase #2	$39.33	8.290%	$42.5905	$42.59	$42.60	$42.60
Purchase #3	$189.45	5.438%	$199.7523	$199.75	$199.75	$199.80
Purchase #4	$120.57	5.384%	$127.0615	$127.06	$127.05	$127.10
Purchase #5	$86.74	9.660%	$95.1191	$95.12	$95.10	$95.10
Purchase #6	$167.42	10.215%	$184.522	$184.52	$184.50	$184.50
Purchase #7	$73.98	8.776%	$80.4725	$80.47	$80.45	$80.50
7 purchase totals =	$888.31		$956.3033	$956.30	$956.25	$956.40