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	$118.71	4.443%	$123.9843	$123.98	$124.00	$124.00
Purchase #2	$71.50	7.214%	$76.658	$76.66	$76.65	$76.70
Purchase #3	$121.86	7.613%	$131.1372	$131.14	$131.15	$131.10
Purchase #4	$240.55	11.476%	$268.1555	$268.16	$268.15	$268.20
Purchase #5	$184.68	6.566%	$196.8061	$196.81	$196.80	$196.80
Purchase #6	$24.88	12.244%	$27.9263	$27.93	$27.95	$27.90
Purchase #7	$131.61	5.542%	$138.9038	$138.90	$138.90	$138.90
7 purchase totals =	$893.79		$963.5712	$963.58	$963.60	$963.60