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	$68.73	13.583%	$78.0656	$78.07	$78.05	$78.10
Purchase #2	$203.63	3.380%	$210.5127	$210.51	$210.50	$210.50
Purchase #3	$32.98	10.351%	$36.3938	$36.39	$36.40	$36.40
Purchase #4	$134.55	8.772%	$146.3527	$146.35	$146.35	$146.40
Purchase #5	$118.73	8.197%	$128.4623	$128.46	$128.45	$128.50
Purchase #6	$214.99	3.290%	$222.0632	$222.06	$222.05	$222.10
Purchase #7	$62.42	3.343%	$64.5067	$64.51	$64.50	$64.50
7 purchase totals =	$836.03		$886.3570	$886.35	$886.30	$886.50