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	$130.95	8.789%	$142.4592	$142.46	$142.45	$142.50
Purchase #2	$220.37	10.475%	$243.4538	$243.45	$243.45	$243.50
Purchase #3	$127.80	9.284%	$139.665	$139.67	$139.65	$139.70
Purchase #4	$112.90	10.818%	$125.1135	$125.11	$125.10	$125.10
Purchase #5	$33.57	5.791%	$35.514	$35.51	$35.50	$35.50
Purchase #6	$66.79	7.602%	$71.8674	$71.87	$71.85	$71.90
Purchase #7	$91.99	13.410%	$104.3259	$104.33	$104.35	$104.30
7 purchase totals =	$784.37		$862.3988	$862.40	$862.35	$862.50