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	$33.64	5.510%	$35.4936	$35.49	$35.50	$35.50
Purchase #2	$159.30	3.369%	$164.6668	$164.67	$164.65	$164.70
Purchase #3	$99.67	6.424%	$106.0728	$106.07	$106.05	$106.10
Purchase #4	$150.32	10.508%	$166.1156	$166.12	$166.10	$166.10
Purchase #5	$203.81	9.128%	$222.4138	$222.41	$222.40	$222.40
Purchase #6	$249.64	9.401%	$273.1087	$273.11	$273.10	$273.10
Purchase #7	$38.40	12.312%	$43.1278	$43.13	$43.15	$43.10
7 purchase totals =	$934.78		$1,010.9991	$1,011.00	$1,010.95	$1,011.00