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	$204.49	9.314%	$223.5362	$223.54	$223.55	$223.50
Purchase #2	$40.46	10.264%	$44.6128	$44.61	$44.60	$44.60
Purchase #3	$128.88	11.790%	$144.075	$144.08	$144.10	$144.10
Purchase #4	$176.88	3.350%	$182.8055	$182.81	$182.80	$182.80
Purchase #5	$148.90	11.280%	$165.6959	$165.70	$165.70	$165.70
Purchase #6	$75.92	3.513%	$78.5871	$78.59	$78.60	$78.60
Purchase #7	$150.47	11.118%	$167.1993	$167.20	$167.20	$167.20
7 purchase totals =	$926.00		$1,006.5118	$1,006.53	$1,006.55	$1,006.50