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	$92.39	11.787%	$103.28	$103.28	$103.30	$103.30
Purchase #2	$99.29	5.774%	$105.023	$105.02	$105.00	$105.00
Purchase #3	$171.46	7.768%	$184.779	$184.78	$184.80	$184.80
Purchase #4	$25.40	5.455%	$26.7856	$26.79	$26.80	$26.80
Purchase #5	$54.76	8.707%	$59.528	$59.53	$59.55	$59.50
Purchase #6	$119.76	5.410%	$126.239	$126.24	$126.25	$126.20
Purchase #7	$164.94	8.444%	$178.8675	$178.87	$178.85	$178.90
7 purchase totals =	$728.00		$784.5021	$784.51	$784.55	$784.50