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	$143.69	5.347%	$151.3731	$151.37	$151.35	$151.40
Purchase #2	$59.88	5.433%	$63.1333	$63.13	$63.15	$63.10
Purchase #3	$128.30	7.377%	$137.7647	$137.76	$137.75	$137.80
Purchase #4	$222.96	4.627%	$233.2764	$233.28	$233.30	$233.30
Purchase #5	$92.28	3.268%	$95.2957	$95.30	$95.30	$95.30
Purchase #6	$167.98	7.456%	$180.5046	$180.50	$180.50	$180.50
Purchase #7	$221.69	6.583%	$236.2839	$236.28	$236.30	$236.30
7 purchase totals =	$1,036.78		$1,097.6317	$1,097.62	$1,097.65	$1,097.70