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	$85.85	4.472%	$89.6892	$89.69	$89.70	$89.70
Purchase #2	$8.63	8.116%	$9.3304	$9.33	$9.35	$9.30
Purchase #3	$117.82	5.136%	$123.8712	$123.87	$123.85	$123.90
Purchase #4	$165.92	8.532%	$180.0763	$180.08	$180.10	$180.10
Purchase #5	$39.93	4.495%	$41.7249	$41.72	$41.70	$41.70
Purchase #6	$55.61	3.704%	$57.6698	$57.67	$57.65	$57.70
Purchase #7	$90.51	13.516%	$102.7433	$102.74	$102.75	$102.70
7 purchase totals =	$564.27		$605.1051	$605.10	$605.10	$605.10