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	$73.63	6.110%	$78.1288	$78.13	$78.15	$78.10
Purchase #2	$40.77	6.646%	$43.4796	$43.48	$43.50	$43.50
Purchase #3	$30.31	6.743%	$32.3538	$32.35	$32.35	$32.40
Purchase #4	$43.88	7.758%	$47.2842	$47.28	$47.30	$47.30
Purchase #5	$242.73	12.824%	$273.8577	$273.86	$273.85	$273.90
Purchase #6	$9.86	4.867%	$10.3399	$10.34	$10.35	$10.30
Purchase #7	$58.41	3.793%	$60.6255	$60.63	$60.65	$60.60
7 purchase totals =	$499.59		$546.0695	$546.07	$546.15	$546.10