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	$130.48	13.293%	$147.8247	$147.82	$147.80	$147.80
Purchase #2	$149.76	10.328%	$165.2272	$165.23	$165.25	$165.20
Purchase #3	$186.81	5.110%	$196.356	$196.36	$196.35	$196.40
Purchase #4	$162.46	9.590%	$178.0399	$178.04	$178.05	$178.00
Purchase #5	$73.98	11.352%	$82.3782	$82.38	$82.40	$82.40
Purchase #6	$135.96	9.485%	$148.8558	$148.86	$148.85	$148.90
Purchase #7	$113.39	9.268%	$123.899	$123.90	$123.90	$123.90
7 purchase totals =	$952.84		$1,042.5808	$1,042.59	$1,042.60	$1,042.60