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	$194.33	6.238%	$206.4523	$206.45	$206.45	$206.50
Purchase #2	$231.30	11.376%	$257.6127	$257.61	$257.60	$257.60
Purchase #3	$180.93	8.821%	$196.8898	$196.89	$196.90	$196.90
Purchase #4	$26.52	8.722%	$28.8331	$28.83	$28.85	$28.80
Purchase #5	$225.85	4.377%	$235.7355	$235.74	$235.75	$235.70
Purchase #6	$17.45	10.499%	$19.2821	$19.28	$19.30	$19.30
Purchase #7	$184.98	8.218%	$200.1817	$200.18	$200.20	$200.20
7 purchase totals =	$1,061.36		$1,144.9872	$1,144.98	$1,145.05	$1,145.00