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	$107.89	3.507%	$111.6737	$111.67	$111.65	$111.70
Purchase #2	$244.78	11.206%	$272.21	$272.21	$272.20	$272.20
Purchase #3	$105.79	12.515%	$119.0296	$119.03	$119.05	$119.00
Purchase #4	$95.29	10.444%	$105.2421	$105.24	$105.25	$105.20
Purchase #5	$245.65	6.583%	$261.8211	$261.82	$261.80	$261.80
Purchase #6	$148.26	12.869%	$167.3396	$167.34	$167.35	$167.30
Purchase #7	$98.27	13.436%	$111.4736	$111.47	$111.45	$111.50
7 purchase totals =	$1,045.93		$1,148.7897	$1,148.78	$1,148.75	$1,148.70