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	$104.57	8.680%	$113.6467	$113.65	$113.65	$113.60
Purchase #2	$96.98	8.225%	$104.9566	$104.96	$104.95	$105.00
Purchase #3	$204.91	6.424%	$218.0734	$218.07	$218.05	$218.10
Purchase #4	$226.65	10.568%	$250.6024	$250.60	$250.60	$250.60
Purchase #5	$250.96	6.351%	$266.8985	$266.90	$266.90	$266.90
Purchase #6	$92.88	7.323%	$99.6816	$99.68	$99.70	$99.70
Purchase #7	$68.78	13.418%	$78.0089	$78.01	$78.00	$78.00
7 purchase totals =	$1,045.73		$1,131.8681	$1,131.87	$1,131.85	$1,131.90