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	$92.89	11.731%	$103.7869	$103.79	$103.80	$103.80
Purchase #2	$199.62	8.738%	$217.0628	$217.06	$217.05	$217.10
Purchase #3	$31.76	11.633%	$35.4546	$35.45	$35.45	$35.50
Purchase #4	$63.51	11.360%	$70.7247	$70.72	$70.70	$70.70
Purchase #5	$146.89	8.435%	$159.2802	$159.28	$159.30	$159.30
Purchase #6	$135.25	5.189%	$142.2681	$142.27	$142.25	$142.30
Purchase #7	$171.29	5.635%	$180.9422	$180.94	$180.95	$180.90
7 purchase totals =	$841.21		$909.5195	$909.51	$909.50	$909.60