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	$133.77	13.293%	$151.552	$151.55	$151.55	$151.60
Purchase #2	$70.77	11.200%	$78.6962	$78.70	$78.70	$78.70
Purchase #3	$224.70	5.623%	$237.3349	$237.33	$237.35	$237.30
Purchase #4	$93.59	6.250%	$99.4394	$99.44	$99.45	$99.40
Purchase #5	$95.44	8.803%	$103.8416	$103.84	$103.85	$103.80
Purchase #6	$126.56	11.502%	$141.1169	$141.12	$141.10	$141.10
Purchase #7	$70.72	9.419%	$77.3811	$77.38	$77.40	$77.40
7 purchase totals =	$815.55		$889.3621	$889.36	$889.40	$889.30