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	$198.56	8.228%	$214.8975	$214.90	$214.90	$214.90
Purchase #2	$35.34	5.768%	$37.3784	$37.38	$37.40	$37.40
Purchase #3	$75.78	11.666%	$84.6205	$84.62	$84.60	$84.60
Purchase #4	$100.75	11.464%	$112.3	$112.30	$112.30	$112.30
Purchase #5	$207.72	4.328%	$216.7101	$216.71	$216.70	$216.70
Purchase #6	$231.34	4.352%	$241.4079	$241.41	$241.40	$241.40
Purchase #7	$206.29	13.423%	$233.9803	$233.98	$234.00	$234.00
7 purchase totals =	$1,055.78		$1,141.2947	$1,141.30	$1,141.30	$1,141.30