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	$180.83	8.645%	$196.4628	$196.46	$196.45	$196.50
Purchase #2	$223.52	7.397%	$240.0538	$240.05	$240.05	$240.10
Purchase #3	$87.97	9.115%	$95.9885	$95.99	$96.00	$96.00
Purchase #4	$231.44	10.569%	$255.9009	$255.90	$255.90	$255.90
Purchase #5	$66.37	8.258%	$71.8508	$71.85	$71.85	$71.90
Purchase #6	$72.96	4.531%	$76.2658	$76.27	$76.25	$76.30
Purchase #7	$76.50	9.484%	$83.7553	$83.76	$83.75	$83.80
7 purchase totals =	$939.59		$1,020.2779	$1,020.28	$1,020.25	$1,020.50