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	$198.86	8.421%	$215.606	$215.61	$215.60	$215.60
Purchase #2	$54.96	7.516%	$59.0908	$59.09	$59.10	$59.10
Purchase #3	$184.60	10.661%	$204.2802	$204.28	$204.30	$204.30
Purchase #4	$238.91	8.457%	$259.1146	$259.11	$259.10	$259.10
Purchase #5	$169.39	3.841%	$175.8963	$175.90	$175.90	$175.90
Purchase #6	$38.68	10.648%	$42.7986	$42.80	$42.80	$42.80
Purchase #7	$227.97	5.309%	$240.0729	$240.07	$240.05	$240.10
7 purchase totals =	$1,113.37		$1,196.8594	$1,196.86	$1,196.85	$1,196.90