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	$119.91	3.316%	$123.8862	$123.89	$123.90	$123.90
Purchase #2	$185.43	13.261%	$210.0199	$210.02	$210.00	$210.00
Purchase #3	$71.56	4.500%	$74.7802	$74.78	$74.80	$74.80
Purchase #4	$100.98	9.480%	$110.5529	$110.55	$110.55	$110.60
Purchase #5	$152.27	12.316%	$171.0236	$171.02	$171.00	$171.00
Purchase #6	$186.82	12.554%	$210.2734	$210.27	$210.25	$210.30
Purchase #7	$158.59	12.206%	$177.9475	$177.95	$177.95	$177.90
7 purchase totals =	$975.56		$1,078.4837	$1,078.48	$1,078.45	$1,078.50