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	$244.32	9.499%	$267.528	$267.53	$267.55	$267.50
Purchase #2	$117.68	4.610%	$123.105	$123.11	$123.10	$123.10
Purchase #3	$57.42	3.516%	$59.4389	$59.44	$59.45	$59.40
Purchase #4	$28.59	5.287%	$30.1016	$30.10	$30.10	$30.10
Purchase #5	$22.95	6.657%	$24.4778	$24.48	$24.50	$24.50
Purchase #6	$118.45	13.363%	$134.2785	$134.28	$134.30	$134.30
Purchase #7	$55.82	5.473%	$58.875	$58.88	$58.90	$58.90
7 purchase totals =	$645.23		$697.8048	$697.82	$697.90	$697.80