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	$95.82	10.653%	$106.0277	$106.03	$106.05	$106.00
Purchase #2	$196.71	8.576%	$213.5798	$213.58	$213.60	$213.60
Purchase #3	$112.41	7.562%	$120.9104	$120.91	$120.90	$120.90
Purchase #4	$226.65	12.586%	$255.1762	$255.18	$255.20	$255.20
Purchase #5	$87.73	13.366%	$99.456	$99.46	$99.45	$99.50
Purchase #6	$83.88	10.641%	$92.8057	$92.81	$92.80	$92.80
Purchase #7	$76.98	10.842%	$85.3262	$85.33	$85.35	$85.30
7 purchase totals =	$880.18		$973.2820	$973.30	$973.35	$973.30