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	$108.77	11.175%	$120.925	$120.93	$120.95	$120.90
Purchase #2	$96.91	13.137%	$109.6411	$109.64	$109.65	$109.60
Purchase #3	$205.50	7.800%	$221.529	$221.53	$221.55	$221.50
Purchase #4	$47.38	5.257%	$49.8708	$49.87	$49.85	$49.90
Purchase #5	$34.88	8.443%	$37.8249	$37.82	$37.80	$37.80
Purchase #6	$178.96	5.341%	$188.5183	$188.52	$188.50	$188.50
Purchase #7	$183.85	11.133%	$204.318	$204.32	$204.30	$204.30
7 purchase totals =	$856.25		$932.6271	$932.63	$932.60	$932.50