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	$100.63	12.597%	$113.3064	$113.31	$113.30	$113.30
Purchase #2	$58.44	6.675%	$62.3409	$62.34	$62.35	$62.30
Purchase #3	$190.95	9.459%	$209.012	$209.01	$209.00	$209.00
Purchase #4	$215.59	8.766%	$234.4886	$234.49	$234.50	$234.50
Purchase #5	$155.57	7.532%	$167.2875	$167.29	$167.30	$167.30
Purchase #6	$137.89	11.326%	$153.5074	$153.51	$153.50	$153.50
Purchase #7	$155.91	7.848%	$168.1458	$168.15	$168.15	$168.10
7 purchase totals =	$1,014.98		$1,108.0886	$1,108.10	$1,108.10	$1,108.00