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	$164.80	12.527%	$185.4445	$185.44	$185.45	$185.40
Purchase #2	$95.30	6.537%	$101.5298	$101.53	$101.55	$101.50
Purchase #3	$31.69	13.225%	$35.881	$35.88	$35.90	$35.90
Purchase #4	$123.25	12.813%	$139.042	$139.04	$139.05	$139.00
Purchase #5	$109.76	9.604%	$120.3014	$120.30	$120.30	$120.30
Purchase #6	$61.87	7.505%	$66.5133	$66.51	$66.50	$66.50
Purchase #7	$158.44	4.489%	$165.5524	$165.55	$165.55	$165.60
7 purchase totals =	$745.11		$814.2644	$814.25	$814.30	$814.20