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	$81.92	4.827%	$85.8743	$85.87	$85.85	$85.90
Purchase #2	$216.74	6.802%	$231.4827	$231.48	$231.50	$231.50
Purchase #3	$153.66	7.232%	$164.7727	$164.77	$164.75	$164.80
Purchase #4	$171.35	12.847%	$193.3633	$193.36	$193.35	$193.40
Purchase #5	$80.30	12.835%	$90.6065	$90.61	$90.60	$90.60
Purchase #6	$41.80	8.853%	$45.5006	$45.50	$45.50	$45.50
Purchase #7	$91.96	4.791%	$96.3658	$96.37	$96.35	$96.40
7 purchase totals =	$837.73		$907.9659	$907.96	$907.90	$908.10