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	$76.51	13.238%	$86.6384	$86.64	$86.65	$86.60
Purchase #2	$185.61	11.133%	$206.274	$206.27	$206.25	$206.30
Purchase #3	$161.97	6.719%	$172.8528	$172.85	$172.85	$172.90
Purchase #4	$182.71	7.405%	$196.2397	$196.24	$196.25	$196.20
Purchase #5	$224.95	9.218%	$245.6859	$245.69	$245.70	$245.70
Purchase #6	$247.53	9.544%	$271.1543	$271.15	$271.15	$271.20
Purchase #7	$99.28	4.735%	$103.9809	$103.98	$104.00	$104.00
7 purchase totals =	$1,178.56		$1,282.8260	$1,282.82	$1,282.85	$1,282.90