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	$83.56	5.217%	$87.9193	$87.92	$87.90	$87.90
Purchase #2	$250.61	8.154%	$271.0447	$271.04	$271.05	$271.00
Purchase #3	$96.76	3.391%	$100.0411	$100.04	$100.05	$100.00
Purchase #4	$187.33	4.731%	$196.1926	$196.19	$196.20	$196.20
Purchase #5	$70.31	8.857%	$76.5374	$76.54	$76.55	$76.50
Purchase #6	$218.46	4.374%	$228.0154	$228.02	$228.00	$228.00
Purchase #7	$52.78	8.549%	$57.2922	$57.29	$57.30	$57.30
7 purchase totals =	$959.81		$1,017.0427	$1,017.04	$1,017.05	$1,016.90