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	$189.89	5.589%	$200.503	$200.50	$200.50	$200.50
Purchase #2	$245.71	13.102%	$277.9029	$277.90	$277.90	$277.90
Purchase #3	$73.60	12.737%	$82.9744	$82.97	$82.95	$83.00
Purchase #4	$166.34	6.197%	$176.6481	$176.65	$176.65	$176.60
Purchase #5	$31.67	4.350%	$33.0476	$33.05	$33.05	$33.00
Purchase #6	$211.39	5.251%	$222.4901	$222.49	$222.50	$222.50
Purchase #7	$95.39	5.299%	$100.4447	$100.44	$100.45	$100.40
7 purchase totals =	$1,013.99		$1,094.0108	$1,094.00	$1,094.00	$1,093.90