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	$17.64	12.290%	$19.808	$19.81	$19.80	$19.80
Purchase #2	$206.65	5.426%	$217.8628	$217.86	$217.85	$217.90
Purchase #3	$208.43	6.676%	$222.3448	$222.34	$222.35	$222.30
Purchase #4	$84.71	5.683%	$89.5241	$89.52	$89.50	$89.50
Purchase #5	$211.49	6.336%	$224.89	$224.89	$224.90	$224.90
Purchase #6	$171.55	7.821%	$184.9669	$184.97	$184.95	$185.00
Purchase #7	$180.34	4.433%	$188.3345	$188.33	$188.35	$188.30
7 purchase totals =	$1,080.81		$1,147.7311	$1,147.72	$1,147.70	$1,147.70