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	$219.55	5.662%	$231.9809	$231.98	$232.00	$232.00
Purchase #2	$189.38	13.404%	$214.7645	$214.76	$214.75	$214.80
Purchase #3	$168.98	6.848%	$180.5518	$180.55	$180.55	$180.60
Purchase #4	$130.29	12.736%	$146.8837	$146.88	$146.90	$146.90
Purchase #5	$35.81	11.724%	$40.0084	$40.01	$40.00	$40.00
Purchase #6	$16.28	7.241%	$17.4588	$17.46	$17.45	$17.50
Purchase #7	$74.53	4.782%	$78.094	$78.09	$78.10	$78.10
7 purchase totals =	$834.82		$909.7421	$909.73	$909.75	$909.90