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	$244.56	7.500%	$262.902	$262.90	$262.90	$262.90
Purchase #2	$150.79	11.546%	$168.2002	$168.20	$168.20	$168.20
Purchase #3	$110.50	6.810%	$118.0251	$118.03	$118.05	$118.00
Purchase #4	$223.66	9.498%	$244.9032	$244.90	$244.90	$244.90
Purchase #5	$104.62	6.229%	$111.1368	$111.14	$111.15	$111.10
Purchase #6	$118.80	7.597%	$127.8252	$127.83	$127.85	$127.80
Purchase #7	$240.81	4.789%	$252.3424	$252.34	$252.35	$252.30
7 purchase totals =	$1,193.74		$1,285.3349	$1,285.34	$1,285.40	$1,285.20