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	$247.27	10.737%	$273.8194	$273.82	$273.80	$273.80
Purchase #2	$225.38	12.630%	$253.8455	$253.85	$253.85	$253.80
Purchase #3	$58.90	6.770%	$62.8875	$62.89	$62.90	$62.90
Purchase #4	$122.45	7.403%	$131.515	$131.52	$131.50	$131.50
Purchase #5	$54.52	10.483%	$60.2353	$60.24	$60.25	$60.20
Purchase #6	$163.44	7.802%	$176.1916	$176.19	$176.20	$176.20
Purchase #7	$59.51	9.546%	$65.1908	$65.19	$65.20	$65.20
7 purchase totals =	$931.47		$1,023.6851	$1,023.70	$1,023.70	$1,023.60