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	$167.97	7.765%	$181.0129	$181.01	$181.00	$181.00
Purchase #2	$64.37	10.382%	$71.0529	$71.05	$71.05	$71.10
Purchase #3	$56.53	5.324%	$59.5397	$59.54	$59.55	$59.50
Purchase #4	$151.28	11.462%	$168.6197	$168.62	$168.60	$168.60
Purchase #5	$126.50	11.698%	$141.298	$141.30	$141.30	$141.30
Purchase #6	$64.54	8.701%	$70.1556	$70.16	$70.15	$70.20
Purchase #7	$50.81	6.284%	$54.0029	$54.00	$54.00	$54.00
7 purchase totals =	$682.00		$745.6817	$745.68	$745.65	$745.70