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	$32.51	6.482%	$34.6173	$34.62	$34.60	$34.60
Purchase #2	$171.72	13.781%	$195.3847	$195.38	$195.40	$195.40
Purchase #3	$173.64	7.275%	$186.2723	$186.27	$186.25	$186.30
Purchase #4	$196.94	12.470%	$221.4984	$221.50	$221.50	$221.50
Purchase #5	$242.47	8.712%	$263.594	$263.59	$263.60	$263.60
Purchase #6	$180.57	4.235%	$188.2171	$188.22	$188.20	$188.20
Purchase #7	$62.60	6.269%	$66.5244	$66.52	$66.50	$66.50
7 purchase totals =	$1,060.45		$1,156.1082	$1,156.10	$1,156.05	$1,156.10