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	$238.75	12.553%	$268.7203	$268.72	$268.70	$268.70
Purchase #2	$196.53	7.742%	$211.7454	$211.75	$211.75	$211.70
Purchase #3	$245.84	7.273%	$263.7199	$263.72	$263.70	$263.70
Purchase #4	$75.54	4.275%	$78.7693	$78.77	$78.75	$78.80
Purchase #5	$11.70	6.624%	$12.475	$12.48	$12.50	$12.50
Purchase #6	$208.43	3.596%	$215.9251	$215.93	$215.95	$215.90
Purchase #7	$36.31	13.398%	$41.1748	$41.17	$41.15	$41.20
7 purchase totals =	$1,013.10		$1,092.5298	$1,092.54	$1,092.50	$1,092.50