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	$25.61	12.816%	$28.8922	$28.89	$28.90	$28.90
Purchase #2	$100.60	12.747%	$113.4235	$113.42	$113.40	$113.40
Purchase #3	$11.41	3.154%	$11.7699	$11.77	$11.75	$11.80
Purchase #4	$12.37	13.803%	$14.0774	$14.08	$14.10	$14.10
Purchase #5	$39.55	7.740%	$42.6112	$42.61	$42.60	$42.60
Purchase #6	$21.52	10.505%	$23.7807	$23.78	$23.80	$23.80
Purchase #7	$201.94	3.855%	$209.7248	$209.72	$209.70	$209.70
7 purchase totals =	$413.00		$444.2797	$444.27	$444.25	$444.30