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	$167.90	7.182%	$179.9586	$179.96	$179.95	$180.00
Purchase #2	$85.30	5.566%	$90.0478	$90.05	$90.05	$90.00
Purchase #3	$169.70	7.158%	$181.8471	$181.85	$181.85	$181.80
Purchase #4	$117.42	8.829%	$127.787	$127.79	$127.80	$127.80
Purchase #5	$172.60	13.542%	$195.9735	$195.97	$195.95	$196.00
Purchase #6	$159.69	12.485%	$179.6273	$179.63	$179.65	$179.60
Purchase #7	$87.60	7.136%	$93.8511	$93.85	$93.85	$93.90
7 purchase totals =	$960.21		$1,049.0924	$1,049.10	$1,049.10	$1,049.10