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	$165.70	11.806%	$185.2625	$185.26	$185.25	$185.30
Purchase #2	$12.41	11.647%	$13.8554	$13.86	$13.85	$13.90
Purchase #3	$36.47	5.575%	$38.5032	$38.50	$38.50	$38.50
Purchase #4	$175.67	7.684%	$189.1685	$189.17	$189.15	$189.20
Purchase #5	$76.77	3.161%	$79.1967	$79.20	$79.20	$79.20
Purchase #6	$90.53	9.775%	$99.3793	$99.38	$99.40	$99.40
Purchase #7	$39.90	6.649%	$42.553	$42.55	$42.55	$42.60
7 purchase totals =	$597.45		$647.9186	$647.92	$647.90	$648.10