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	$200.81	9.837%	$220.5637	$220.56	$220.55	$220.60
Purchase #2	$81.36	10.685%	$90.0533	$90.05	$90.05	$90.10
Purchase #3	$203.27	9.849%	$223.2901	$223.29	$223.30	$223.30
Purchase #4	$176.60	13.676%	$200.7518	$200.75	$200.75	$200.80
Purchase #5	$66.76	4.717%	$69.9091	$69.91	$69.90	$69.90
Purchase #6	$59.59	9.840%	$65.4537	$65.45	$65.45	$65.50
Purchase #7	$225.60	6.513%	$240.2933	$240.29	$240.30	$240.30
7 purchase totals =	$1,013.99		$1,110.3150	$1,110.30	$1,110.30	$1,110.50