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	$118.83	7.633%	$127.9003	$127.90	$127.90	$127.90
Purchase #2	$248.37	7.362%	$266.655	$266.66	$266.65	$266.70
Purchase #3	$169.87	9.170%	$185.4471	$185.45	$185.45	$185.40
Purchase #4	$78.29	5.541%	$82.628	$82.63	$82.65	$82.60
Purchase #5	$114.30	8.398%	$123.8989	$123.90	$123.90	$123.90
Purchase #6	$165.35	8.126%	$178.7863	$178.79	$178.80	$178.80
Purchase #7	$177.27	12.239%	$198.9661	$198.97	$198.95	$199.00
7 purchase totals =	$1,072.28		$1,164.2817	$1,164.30	$1,164.30	$1,164.30