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	$213.87	11.648%	$238.7816	$238.78	$238.80	$238.80
Purchase #2	$175.89	6.235%	$186.8567	$186.86	$186.85	$186.90
Purchase #3	$165.81	3.389%	$171.4293	$171.43	$171.45	$171.40
Purchase #4	$59.71	6.817%	$63.7804	$63.78	$63.80	$63.80
Purchase #5	$129.94	11.228%	$144.5297	$144.53	$144.55	$144.50
Purchase #6	$94.33	4.678%	$98.7428	$98.74	$98.75	$98.70
Purchase #7	$219.49	11.541%	$244.8213	$244.82	$244.80	$244.80
7 purchase totals =	$1,059.04		$1,148.9418	$1,148.94	$1,149.00	$1,148.90