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	$195.42	13.846%	$222.4779	$222.48	$222.50	$222.50
Purchase #2	$24.99	4.442%	$26.1001	$26.10	$26.10	$26.10
Purchase #3	$39.49	3.694%	$40.9488	$40.95	$40.95	$40.90
Purchase #4	$182.66	4.435%	$190.761	$190.76	$190.75	$190.80
Purchase #5	$219.36	12.222%	$246.1702	$246.17	$246.15	$246.20
Purchase #6	$225.68	10.737%	$249.9113	$249.91	$249.90	$249.90
Purchase #7	$73.54	7.317%	$78.9209	$78.92	$78.90	$78.90
7 purchase totals =	$961.14		$1,055.2902	$1,055.29	$1,055.25	$1,055.30