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	$52.84	9.587%	$57.9058	$57.91	$57.90	$57.90
Purchase #2	$238.73	6.372%	$253.9419	$253.94	$253.95	$253.90
Purchase #3	$200.59	5.140%	$210.9003	$210.90	$210.90	$210.90
Purchase #4	$242.52	5.374%	$255.553	$255.55	$255.55	$255.60
Purchase #5	$233.89	5.119%	$245.8628	$245.86	$245.85	$245.90
Purchase #6	$30.62	4.811%	$32.0931	$32.09	$32.10	$32.10
Purchase #7	$172.91	3.297%	$178.6108	$178.61	$178.60	$178.60
7 purchase totals =	$1,172.10		$1,234.8677	$1,234.86	$1,234.85	$1,234.90