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	$208.51	11.132%	$231.7213	$231.72	$231.70	$231.70
Purchase #2	$145.60	4.305%	$151.8681	$151.87	$151.85	$151.90
Purchase #3	$250.33	8.170%	$270.782	$270.78	$270.80	$270.80
Purchase #4	$85.98	4.679%	$90.003	$90.00	$90.00	$90.00
Purchase #5	$30.27	8.172%	$32.7437	$32.74	$32.75	$32.70
Purchase #6	$225.70	3.181%	$232.8795	$232.88	$232.90	$232.90
Purchase #7	$75.61	5.402%	$79.6945	$79.69	$79.70	$79.70
7 purchase totals =	$1,022.00		$1,089.6921	$1,089.68	$1,089.70	$1,089.70