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	$245.46	4.118%	$255.568	$255.57	$255.55	$255.60
Purchase #2	$76.82	4.427%	$80.2208	$80.22	$80.20	$80.20
Purchase #3	$138.55	3.112%	$142.8617	$142.86	$142.85	$142.90
Purchase #4	$149.47	4.687%	$156.4757	$156.48	$156.50	$156.50
Purchase #5	$244.79	11.152%	$272.089	$272.09	$272.10	$272.10
Purchase #6	$136.40	8.396%	$147.8521	$147.85	$147.85	$147.90
Purchase #7	$19.72	10.802%	$21.8502	$21.85	$21.85	$21.90
7 purchase totals =	$1,011.21		$1,076.9175	$1,076.92	$1,076.90	$1,077.10