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	$221.73	4.201%	$231.0449	$231.04	$231.05	$231.00
Purchase #2	$119.54	4.429%	$124.8344	$124.83	$124.85	$124.80
Purchase #3	$169.27	9.505%	$185.3591	$185.36	$185.35	$185.40
Purchase #4	$190.27	11.260%	$211.6944	$211.69	$211.70	$211.70
Purchase #5	$56.40	12.363%	$63.3727	$63.37	$63.35	$63.40
Purchase #6	$154.87	12.728%	$174.5819	$174.58	$174.60	$174.60
Purchase #7	$145.53	4.194%	$151.6335	$151.63	$151.65	$151.60
7 purchase totals =	$1,057.61		$1,142.5209	$1,142.50	$1,142.55	$1,142.50