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	$5.43	7.552%	$5.8401	$5.84	$5.85	$5.80
Purchase #2	$90.48	5.670%	$95.6102	$95.61	$95.60	$95.60
Purchase #3	$95.82	4.400%	$100.0361	$100.04	$100.05	$100.00
Purchase #4	$73.53	6.348%	$78.1977	$78.20	$78.20	$78.20
Purchase #5	$198.44	8.227%	$214.7657	$214.77	$214.75	$214.80
Purchase #6	$71.57	9.367%	$78.274	$78.27	$78.25	$78.30
Purchase #7	$166.46	11.814%	$186.1256	$186.13	$186.15	$186.10
7 purchase totals =	$701.73		$758.8494	$758.86	$758.85	$758.80