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	$66.51	11.373%	$74.0742	$74.07	$74.05	$74.10
Purchase #2	$87.69	11.199%	$97.5104	$97.51	$97.50	$97.50
Purchase #3	$233.63	9.483%	$255.7851	$255.79	$255.80	$255.80
Purchase #4	$135.26	12.676%	$152.4056	$152.41	$152.40	$152.40
Purchase #5	$165.40	10.268%	$182.3833	$182.38	$182.40	$182.40
Purchase #6	$33.82	13.722%	$38.4608	$38.46	$38.45	$38.50
Purchase #7	$182.62	9.727%	$200.3834	$200.38	$200.40	$200.40
7 purchase totals =	$904.93		$1,001.0028	$1,001.00	$1,001.00	$1,001.10