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	$83.81	9.669%	$91.9136	$91.91	$91.90	$91.90
Purchase #2	$199.34	3.147%	$205.6132	$205.61	$205.60	$205.60
Purchase #3	$160.93	11.838%	$179.9809	$179.98	$180.00	$180.00
Purchase #4	$73.94	11.120%	$82.1621	$82.16	$82.15	$82.20
Purchase #5	$152.54	7.418%	$163.8554	$163.86	$163.85	$163.90
Purchase #6	$78.58	8.849%	$85.5335	$85.53	$85.55	$85.50
Purchase #7	$197.28	12.814%	$222.5595	$222.56	$222.55	$222.60
7 purchase totals =	$946.42		$1,031.6182	$1,031.61	$1,031.60	$1,031.70