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	$69.67	10.366%	$76.892	$76.89	$76.90	$76.90
Purchase #2	$181.44	10.239%	$200.0176	$200.02	$200.00	$200.00
Purchase #3	$152.55	12.588%	$171.753	$171.75	$171.75	$171.80
Purchase #4	$226.25	6.864%	$241.7798	$241.78	$241.80	$241.80
Purchase #5	$151.71	10.281%	$167.3073	$167.31	$167.30	$167.30
Purchase #6	$60.97	4.650%	$63.8051	$63.81	$63.80	$63.80
Purchase #7	$189.75	4.815%	$198.8865	$198.89	$198.90	$198.90
7 purchase totals =	$1,032.34		$1,120.4413	$1,120.45	$1,120.45	$1,120.50