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	$58.45	11.656%	$65.2629	$65.26	$65.25	$65.30
Purchase #2	$118.51	4.229%	$123.5218	$123.52	$123.50	$123.50
Purchase #3	$188.52	10.525%	$208.3617	$208.36	$208.35	$208.40
Purchase #4	$69.67	3.828%	$72.337	$72.34	$72.35	$72.30
Purchase #5	$170.75	3.244%	$176.2891	$176.29	$176.30	$176.30
Purchase #6	$227.73	6.797%	$243.2088	$243.21	$243.20	$243.20
Purchase #7	$105.93	13.627%	$120.3651	$120.37	$120.35	$120.40
7 purchase totals =	$939.56		$1,009.3464	$1,009.35	$1,009.30	$1,009.40