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	$114.29	4.384%	$119.3005	$119.30	$119.30	$119.30
Purchase #2	$162.49	6.431%	$172.9397	$172.94	$172.95	$172.90
Purchase #3	$195.76	12.384%	$220.0029	$220.00	$220.00	$220.00
Purchase #4	$98.58	8.488%	$106.9475	$106.95	$106.95	$106.90
Purchase #5	$223.73	8.660%	$243.105	$243.11	$243.10	$243.10
Purchase #6	$150.76	5.861%	$159.596	$159.60	$159.60	$159.60
Purchase #7	$84.80	6.299%	$90.1416	$90.14	$90.15	$90.10
7 purchase totals =	$1,030.41		$1,112.0332	$1,112.04	$1,112.05	$1,111.90