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	$216.53	5.366%	$228.149	$228.15	$228.15	$228.10
Purchase #2	$168.74	6.567%	$179.8212	$179.82	$179.80	$179.80
Purchase #3	$5.76	3.165%	$5.9423	$5.94	$5.95	$5.90
Purchase #4	$111.77	10.488%	$123.4924	$123.49	$123.50	$123.50
Purchase #5	$176.77	11.110%	$196.4091	$196.41	$196.40	$196.40
Purchase #6	$246.65	4.553%	$257.88	$257.88	$257.90	$257.90
Purchase #7	$25.96	11.567%	$28.9628	$28.96	$28.95	$29.00
7 purchase totals =	$952.18		$1,020.6568	$1,020.65	$1,020.65	$1,020.60