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	$30.34	3.484%	$31.397	$31.40	$31.40	$31.40
Purchase #2	$161.84	10.627%	$179.0387	$179.04	$179.05	$179.00
Purchase #3	$178.71	6.489%	$190.3065	$190.31	$190.30	$190.30
Purchase #4	$111.89	5.416%	$117.95	$117.95	$117.95	$118.00
Purchase #5	$66.33	9.289%	$72.4914	$72.49	$72.50	$72.50
Purchase #6	$167.56	4.825%	$175.6448	$175.64	$175.65	$175.60
Purchase #7	$198.97	6.303%	$211.5111	$211.51	$211.50	$211.50
7 purchase totals =	$915.64		$978.3395	$978.34	$978.35	$978.30