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	$162.68	10.656%	$180.0152	$180.02	$180.00	$180.00
Purchase #2	$20.60	5.703%	$21.7748	$21.77	$21.75	$21.80
Purchase #3	$236.53	11.712%	$264.2324	$264.23	$264.25	$264.20
Purchase #4	$78.47	12.874%	$88.5722	$88.57	$88.55	$88.60
Purchase #5	$85.39	10.562%	$94.4089	$94.41	$94.40	$94.40
Purchase #6	$75.82	3.473%	$78.4532	$78.45	$78.45	$78.50
Purchase #7	$29.68	7.745%	$31.9787	$31.98	$32.00	$32.00
7 purchase totals =	$689.17		$759.4354	$759.43	$759.40	$759.50