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	$168.47	5.198%	$177.2271	$177.23	$177.25	$177.20
Purchase #2	$99.72	13.785%	$113.4664	$113.47	$113.45	$113.50
Purchase #3	$246.50	8.663%	$267.8543	$267.85	$267.85	$267.90
Purchase #4	$177.88	10.661%	$196.8438	$196.84	$196.85	$196.80
Purchase #5	$224.92	9.182%	$245.5722	$245.57	$245.55	$245.60
Purchase #6	$240.35	13.872%	$273.6914	$273.69	$273.70	$273.70
Purchase #7	$64.49	10.564%	$71.3027	$71.30	$71.30	$71.30
7 purchase totals =	$1,222.33		$1,345.9579	$1,345.95	$1,345.95	$1,346.00