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	$196.90	13.384%	$223.2531	$223.25	$223.25	$223.30
Purchase #2	$99.46	10.316%	$109.7203	$109.72	$109.70	$109.70
Purchase #3	$57.86	3.716%	$60.0101	$60.01	$60.00	$60.00
Purchase #4	$60.61	6.811%	$64.7381	$64.74	$64.75	$64.70
Purchase #5	$236.57	13.762%	$269.1268	$269.13	$269.15	$269.10
Purchase #6	$243.82	4.115%	$253.8532	$253.85	$253.85	$253.90
Purchase #7	$51.85	7.132%	$55.5479	$55.55	$55.55	$55.50
7 purchase totals =	$947.07		$1,036.2495	$1,036.25	$1,036.25	$1,036.20