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	$221.89	11.818%	$248.113	$248.11	$248.10	$248.10
Purchase #2	$229.96	13.722%	$261.5151	$261.52	$261.50	$261.50
Purchase #3	$136.76	10.134%	$150.6193	$150.62	$150.60	$150.60
Purchase #4	$157.81	6.310%	$167.7678	$167.77	$167.75	$167.80
Purchase #5	$154.82	11.264%	$172.2589	$172.26	$172.25	$172.30
Purchase #6	$221.77	6.642%	$236.5	$236.50	$236.50	$236.50
Purchase #7	$147.75	9.856%	$162.3122	$162.31	$162.30	$162.30
7 purchase totals =	$1,270.76		$1,399.0863	$1,399.09	$1,399.00	$1,399.10