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	$99.56	9.166%	$108.6857	$108.69	$108.70	$108.70
Purchase #2	$101.87	12.276%	$114.3756	$114.38	$114.40	$114.40
Purchase #3	$56.29	9.255%	$61.4996	$61.50	$61.50	$61.50
Purchase #4	$29.96	9.465%	$32.7957	$32.80	$32.80	$32.80
Purchase #5	$168.73	12.276%	$189.4433	$189.44	$189.45	$189.40
Purchase #6	$146.46	11.238%	$162.9192	$162.92	$162.90	$162.90
Purchase #7	$61.99	8.513%	$67.2672	$67.27	$67.25	$67.30
7 purchase totals =	$664.86		$736.9863	$737.00	$737.00	$737.00