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	$90.25	5.715%	$95.4078	$95.41	$95.40	$95.40
Purchase #2	$104.62	4.231%	$109.0465	$109.05	$109.05	$109.00
Purchase #3	$212.53	4.275%	$221.6157	$221.62	$221.60	$221.60
Purchase #4	$47.80	13.772%	$54.383	$54.38	$54.40	$54.40
Purchase #5	$213.74	13.110%	$241.7613	$241.76	$241.75	$241.80
Purchase #6	$131.89	8.612%	$143.2484	$143.25	$143.25	$143.20
Purchase #7	$234.33	6.448%	$249.4396	$249.44	$249.45	$249.40
7 purchase totals =	$1,035.16		$1,114.9023	$1,114.91	$1,114.90	$1,114.80