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	$85.35	12.234%	$95.7917	$95.79	$95.80	$95.80
Purchase #2	$72.42	7.828%	$78.089	$78.09	$78.10	$78.10
Purchase #3	$64.87	11.623%	$72.4098	$72.41	$72.40	$72.40
Purchase #4	$154.59	7.305%	$165.8828	$165.88	$165.90	$165.90
Purchase #5	$136.50	8.179%	$147.6643	$147.66	$147.65	$147.70
Purchase #6	$100.99	11.358%	$112.4604	$112.46	$112.45	$112.50
Purchase #7	$31.83	10.164%	$35.0652	$35.07	$35.05	$35.10
7 purchase totals =	$646.55		$707.3632	$707.36	$707.35	$707.50