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	$89.78	4.609%	$93.918	$93.92	$93.90	$93.90
Purchase #2	$145.57	7.528%	$156.5285	$156.53	$156.55	$156.50
Purchase #3	$24.27	8.427%	$26.3152	$26.32	$26.30	$26.30
Purchase #4	$75.60	4.303%	$78.8531	$78.85	$78.85	$78.90
Purchase #5	$126.63	8.458%	$137.3404	$137.34	$137.35	$137.30
Purchase #6	$38.86	6.749%	$41.4827	$41.48	$41.50	$41.50
Purchase #7	$29.26	6.158%	$31.0618	$31.06	$31.05	$31.10
7 purchase totals =	$529.97		$565.4997	$565.50	$565.50	$565.50