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	$122.60	7.247%	$131.4848	$131.48	$131.50	$131.50
Purchase #2	$17.86	5.175%	$18.7843	$18.78	$18.80	$18.80
Purchase #3	$210.76	10.859%	$233.6464	$233.65	$233.65	$233.60
Purchase #4	$10.51	12.330%	$11.8059	$11.81	$11.80	$11.80
Purchase #5	$191.83	4.553%	$200.564	$200.56	$200.55	$200.60
Purchase #6	$78.92	5.193%	$83.0183	$83.02	$83.00	$83.00
Purchase #7	$60.90	11.412%	$67.8499	$67.85	$67.85	$67.80
7 purchase totals =	$693.38		$747.1536	$747.15	$747.15	$747.10