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	$172.46	11.111%	$191.622	$191.62	$191.60	$191.60
Purchase #2	$44.85	12.838%	$50.6078	$50.61	$50.60	$50.60
Purchase #3	$56.88	5.104%	$59.7832	$59.78	$59.80	$59.80
Purchase #4	$113.62	7.358%	$121.9802	$121.98	$122.00	$122.00
Purchase #5	$150.29	11.769%	$167.9776	$167.98	$168.00	$168.00
Purchase #6	$142.27	6.251%	$151.1633	$151.16	$151.15	$151.20
Purchase #7	$100.50	13.564%	$114.1318	$114.13	$114.15	$114.10
7 purchase totals =	$780.87		$857.2659	$857.26	$857.30	$857.30