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	$151.66	10.289%	$167.2643	$167.26	$167.25	$167.30
Purchase #2	$187.43	10.176%	$206.5029	$206.50	$206.50	$206.50
Purchase #3	$82.55	11.839%	$92.3231	$92.32	$92.30	$92.30
Purchase #4	$36.27	9.770%	$39.8136	$39.81	$39.80	$39.80
Purchase #5	$221.76	11.662%	$247.6217	$247.62	$247.60	$247.60
Purchase #6	$33.99	10.766%	$37.6494	$37.65	$37.65	$37.60
Purchase #7	$231.91	4.551%	$242.4642	$242.46	$242.45	$242.50
7 purchase totals =	$945.57		$1,033.6392	$1,033.62	$1,033.55	$1,033.60