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	$97.62	12.225%	$109.554	$109.55	$109.55	$109.60
Purchase #2	$40.96	5.407%	$43.1747	$43.17	$43.15	$43.20
Purchase #3	$158.53	5.528%	$167.2935	$167.29	$167.30	$167.30
Purchase #4	$38.59	11.374%	$42.9792	$42.98	$43.00	$43.00
Purchase #5	$36.40	4.198%	$37.9281	$37.93	$37.95	$37.90
Purchase #6	$248.41	3.685%	$257.5639	$257.56	$257.55	$257.60
Purchase #7	$20.79	12.670%	$23.4241	$23.42	$23.40	$23.40
7 purchase totals =	$641.30		$681.9175	$681.90	$681.90	$682.00