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	$165.62	10.705%	$183.3496	$183.35	$183.35	$183.30
Purchase #2	$38.42	6.439%	$40.8939	$40.89	$40.90	$40.90
Purchase #3	$8.65	11.463%	$9.6415	$9.64	$9.65	$9.60
Purchase #4	$87.66	13.451%	$99.4511	$99.45	$99.45	$99.50
Purchase #5	$35.34	6.589%	$37.6686	$37.67	$37.65	$37.70
Purchase #6	$10.53	6.677%	$11.2331	$11.23	$11.25	$11.20
Purchase #7	$59.87	9.598%	$65.6163	$65.62	$65.60	$65.60
7 purchase totals =	$406.09		$447.8541	$447.85	$447.85	$447.80