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	$205.35	8.405%	$222.6097	$222.61	$222.60	$222.60
Purchase #2	$66.32	9.742%	$72.7809	$72.78	$72.80	$72.80
Purchase #3	$211.61	12.631%	$238.3385	$238.34	$238.35	$238.30
Purchase #4	$154.35	3.846%	$160.2863	$160.29	$160.30	$160.30
Purchase #5	$124.63	8.752%	$135.5376	$135.54	$135.55	$135.50
Purchase #6	$176.98	8.696%	$192.3702	$192.37	$192.35	$192.40
Purchase #7	$100.68	6.167%	$106.8889	$106.89	$106.90	$106.90
7 purchase totals =	$1,039.92		$1,128.8121	$1,128.82	$1,128.85	$1,128.80