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	$203.47	12.814%	$229.5426	$229.54	$229.55	$229.50
Purchase #2	$99.79	8.245%	$108.0177	$108.02	$108.00	$108.00
Purchase #3	$86.52	6.460%	$92.1092	$92.11	$92.10	$92.10
Purchase #4	$61.55	10.114%	$67.7752	$67.78	$67.80	$67.80
Purchase #5	$102.41	6.264%	$108.825	$108.83	$108.85	$108.80
Purchase #6	$66.87	5.854%	$70.7846	$70.78	$70.80	$70.80
Purchase #7	$227.43	12.242%	$255.272	$255.27	$255.25	$255.30
7 purchase totals =	$848.04		$932.3263	$932.33	$932.35	$932.30