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	$61.33	3.693%	$63.5949	$63.59	$63.60	$63.60
Purchase #2	$242.80	12.654%	$273.5239	$273.52	$273.50	$273.50
Purchase #3	$142.28	4.641%	$148.8832	$148.88	$148.90	$148.90
Purchase #4	$73.53	6.783%	$78.5175	$78.52	$78.50	$78.50
Purchase #5	$118.80	9.665%	$130.282	$130.28	$130.30	$130.30
Purchase #6	$123.61	9.368%	$135.1898	$135.19	$135.20	$135.20
Purchase #7	$127.51	8.362%	$138.1724	$138.17	$138.15	$138.20
7 purchase totals =	$889.86		$968.1637	$968.15	$968.15	$968.20