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	$52.76	13.245%	$59.7481	$59.75	$59.75	$59.70
Purchase #2	$136.38	6.343%	$145.0306	$145.03	$145.05	$145.00
Purchase #3	$72.61	7.269%	$77.888	$77.89	$77.90	$77.90
Purchase #4	$110.85	3.273%	$114.4781	$114.48	$114.50	$114.50
Purchase #5	$72.79	8.443%	$78.9357	$78.94	$78.95	$78.90
Purchase #6	$25.28	11.805%	$28.2643	$28.26	$28.25	$28.30
Purchase #7	$189.65	10.559%	$209.6751	$209.68	$209.70	$209.70
7 purchase totals =	$660.32		$714.0199	$714.03	$714.10	$714.00