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	$189.29	8.572%	$205.5159	$205.52	$205.50	$205.50
Purchase #2	$51.75	8.766%	$56.2864	$56.29	$56.30	$56.30
Purchase #3	$164.38	6.496%	$175.0581	$175.06	$175.05	$175.10
Purchase #4	$203.57	4.614%	$212.9627	$212.96	$212.95	$213.00
Purchase #5	$100.69	4.700%	$105.4224	$105.42	$105.40	$105.40
Purchase #6	$64.38	5.346%	$67.8218	$67.82	$67.80	$67.80
Purchase #7	$238.46	4.330%	$248.7853	$248.79	$248.80	$248.80
7 purchase totals =	$1,012.52		$1,071.8526	$1,071.86	$1,071.80	$1,071.90