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	$132.45	9.770%	$145.3904	$145.39	$145.40	$145.40
Purchase #2	$121.75	7.112%	$130.4089	$130.41	$130.40	$130.40
Purchase #3	$127.93	5.263%	$134.663	$134.66	$134.65	$134.70
Purchase #4	$91.87	4.466%	$95.9729	$95.97	$95.95	$96.00
Purchase #5	$69.73	3.397%	$72.0987	$72.10	$72.10	$72.10
Purchase #6	$82.99	8.466%	$90.0159	$90.02	$90.00	$90.00
Purchase #7	$29.66	7.412%	$31.8584	$31.86	$31.85	$31.90
7 purchase totals =	$656.38		$700.4082	$700.41	$700.35	$700.50