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	$74.91	10.705%	$82.9291	$82.93	$82.95	$82.90
Purchase #2	$247.95	6.661%	$264.4659	$264.47	$264.45	$264.50
Purchase #3	$6.99	6.821%	$7.4668	$7.47	$7.45	$7.50
Purchase #4	$13.82	3.212%	$14.2639	$14.26	$14.25	$14.30
Purchase #5	$61.74	4.787%	$64.6955	$64.70	$64.70	$64.70
Purchase #6	$215.61	4.763%	$225.8795	$225.88	$225.90	$225.90
Purchase #7	$37.72	7.531%	$40.5607	$40.56	$40.55	$40.60
7 purchase totals =	$658.74		$700.2614	$700.27	$700.25	$700.40