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	$250.89	11.768%	$280.4147	$280.41	$280.40	$280.40
Purchase #2	$58.58	4.502%	$61.2173	$61.22	$61.20	$61.20
Purchase #3	$188.37	10.736%	$208.5934	$208.59	$208.60	$208.60
Purchase #4	$36.60	12.393%	$41.1358	$41.14	$41.15	$41.10
Purchase #5	$51.48	6.597%	$54.8761	$54.88	$54.90	$54.90
Purchase #6	$201.94	11.649%	$225.464	$225.46	$225.45	$225.50
Purchase #7	$247.68	3.612%	$256.6262	$256.63	$256.65	$256.60
7 purchase totals =	$1,035.54		$1,128.3275	$1,128.33	$1,128.35	$1,128.30