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	$191.66	7.555%	$206.1399	$206.14	$206.15	$206.10
Purchase #2	$108.39	12.119%	$121.5258	$121.53	$121.55	$121.50
Purchase #3	$172.39	10.143%	$189.8755	$189.88	$189.90	$189.90
Purchase #4	$161.80	4.279%	$168.7234	$168.72	$168.70	$168.70
Purchase #5	$100.76	3.687%	$104.475	$104.48	$104.50	$104.50
Purchase #6	$108.86	13.855%	$123.9426	$123.94	$123.95	$123.90
Purchase #7	$128.49	3.661%	$133.194	$133.19	$133.20	$133.20
7 purchase totals =	$972.35		$1,047.8762	$1,047.88	$1,047.95	$1,047.80