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	$155.86	10.475%	$172.1863	$172.19	$172.20	$172.20
Purchase #2	$114.94	11.403%	$128.0466	$128.05	$128.05	$128.00
Purchase #3	$187.39	11.297%	$208.5594	$208.56	$208.55	$208.60
Purchase #4	$159.27	5.569%	$168.1397	$168.14	$168.15	$168.10
Purchase #5	$119.35	7.478%	$128.275	$128.28	$128.30	$128.30
Purchase #6	$140.83	13.529%	$159.8829	$159.88	$159.90	$159.90
Purchase #7	$78.95	10.365%	$87.1332	$87.13	$87.15	$87.10
7 purchase totals =	$956.59		$1,052.2231	$1,052.23	$1,052.30	$1,052.20