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	$182.44	7.566%	$196.2434	$196.24	$196.25	$196.20
Purchase #2	$57.53	5.772%	$60.8506	$60.85	$60.85	$60.90
Purchase #3	$59.63	12.610%	$67.1493	$67.15	$67.15	$67.10
Purchase #4	$120.48	10.373%	$132.9774	$132.98	$133.00	$133.00
Purchase #5	$83.89	11.574%	$93.5994	$93.60	$93.60	$93.60
Purchase #6	$27.55	8.508%	$29.894	$29.89	$29.90	$29.90
Purchase #7	$139.29	6.174%	$147.8898	$147.89	$147.90	$147.90
7 purchase totals =	$670.81		$728.6039	$728.60	$728.65	$728.60