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	$112.78	9.430%	$123.4152	$123.42	$123.40	$123.40
Purchase #2	$93.59	7.694%	$100.7908	$100.79	$100.80	$100.80
Purchase #3	$130.35	3.470%	$134.8731	$134.87	$134.85	$134.90
Purchase #4	$84.38	6.600%	$89.9491	$89.95	$89.95	$89.90
Purchase #5	$88.92	12.187%	$99.7567	$99.76	$99.75	$99.80
Purchase #6	$16.61	6.872%	$17.7514	$17.75	$17.75	$17.80
Purchase #7	$150.54	5.323%	$158.5532	$158.55	$158.55	$158.60
7 purchase totals =	$677.17		$725.0895	$725.09	$725.05	$725.20