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	$105.69	9.340%	$115.5614	$115.56	$115.55	$115.60
Purchase #2	$114.37	9.703%	$125.4673	$125.47	$125.45	$125.50
Purchase #3	$149.59	12.764%	$168.6837	$168.68	$168.70	$168.70
Purchase #4	$31.44	4.663%	$32.906	$32.91	$32.90	$32.90
Purchase #5	$108.82	13.863%	$123.9057	$123.91	$123.90	$123.90
Purchase #6	$222.41	4.285%	$231.9403	$231.94	$231.95	$231.90
Purchase #7	$181.72	3.387%	$187.8749	$187.87	$187.85	$187.90
7 purchase totals =	$914.04		$986.3393	$986.34	$986.30	$986.40