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	$84.73	9.534%	$92.8082	$92.81	$92.80	$92.80
Purchase #2	$165.67	12.820%	$186.9089	$186.91	$186.90	$186.90
Purchase #3	$43.49	12.343%	$48.858	$48.86	$48.85	$48.90
Purchase #4	$196.61	12.532%	$221.2492	$221.25	$221.25	$221.20
Purchase #5	$162.44	7.217%	$174.1633	$174.16	$174.15	$174.20
Purchase #6	$73.26	12.568%	$82.4673	$82.47	$82.45	$82.50
Purchase #7	$196.83	7.163%	$210.9289	$210.93	$210.95	$210.90
7 purchase totals =	$923.03		$1,017.3838	$1,017.39	$1,017.35	$1,017.40