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	$31.44	12.767%	$35.4539	$35.45	$35.45	$35.50
Purchase #2	$136.57	5.828%	$144.5293	$144.53	$144.55	$144.50
Purchase #3	$63.85	8.131%	$69.0416	$69.04	$69.05	$69.00
Purchase #4	$103.59	5.372%	$109.1549	$109.15	$109.15	$109.20
Purchase #5	$185.38	6.736%	$197.8672	$197.87	$197.85	$197.90
Purchase #6	$154.89	6.773%	$165.3807	$165.38	$165.40	$165.40
Purchase #7	$75.89	6.649%	$80.9359	$80.94	$80.95	$80.90
7 purchase totals =	$751.61		$802.3635	$802.36	$802.40	$802.40